CHAPTER XVIII

MODES OF MAMMALIAN EVOLUTION

Throughout this book the theory of evolution has been taken for granted, as it seemed superfluous to present an outline of the evidence upon which that theory rests. “Descent with modification” is now accepted among naturalists with almost complete unanimity, but, unfortunately or otherwise, this general agreement does not extend beyond the point of believing that the present organic world has arisen by descent from simpler and simpler forms. The application of the theory to concrete cases is beset with grave difficulties and gives rise to the most divergent views. The uninitiated reader who takes up a treatise upon some animal group may well be surprised to see the apparently minute accuracy with which the genealogy of the series is set forth and the complex relationships of its members marshalled in orderly array. Another treatise on the same subject, however, while agreeing perfectly with the first as to the facts, will contradict its conclusions in almost every particular. Indeed, so notorious did this become, that “phylogenetic trees” were rather a laughing-stock, and most naturalists lost interest in the problems of phylogeny and turned to fields that seemed more promising.

To some extent, this almost hopeless divergence is inherent in the very nature of the problem, which deals with the value of evidence and the balancing of probabilities, as to which men must be expected to differ; but there is another and more potent cause of the discrepancy. When the contradictory schemes are analyzed, it is seen that each is founded upon certain assumptions regarding the evolutionary process, assumptions which are generally implicit and often apparently unconscious. In the present state of knowledge, these postulates are, for the most part, matters of judgment, incapable of definite proof, and they appeal with very different force to different minds; what to one seems almost self-evident, another regards as all but impossible. It will, however, be of service to examine such of these postulates as are involved in mammalian history.

It is quite impracticable to construct a genetic series without making certain assumptions as to the manner in which the developmental process operated and the kinds of modification that actually did occur. In the preceding chapters, which deal with the evolutionary history of various mammalian groups, it was repeatedly stated that, of two contemporary genera, one was to be taken as the ancestor of some later form and the other regarded as a collateral branch, but it was also pointed out that in certain cases, palæontologists differed more or less decidedly as to the proper interpretation of the facts; it is just this lack of agreement as to the modes and processes of change that forms the root of the difficulty.

There are instructive analogies between the history, aims and methods of comparative philology, on the one hand, and zoölogy, on the other. In both sciences the attempt is made to trace the development of the modern from the ancient, to demonstrate the common origin of things which are now widely separated and differ in all obvious characteristics, and to determine the manner in which these cumulative modifications have been effected. At the present time zoölogy is still far behind the science of language with regard to the solution of many of these kindred problems and has hardly advanced beyond the stage which called forth Voltaire’s famous sneer: “L’étymologie est une science ou les voyelles ne font rien et les consonnes fort peu de chose.” Many of the animal genealogies which have been proposed have no better foundation than the “guessing etymologies” of the eighteenth century, and for exactly the same reason. Just as the old etymologists made their derivations upon the basis of a likeness of sound and meaning in the words compared, so the modern zoölogist, in attempting to trace the relationships of animals, must proceed by balancing their similarities and differences of structure. The etymologist had no sure test for distinguishing a true derivation from a plausible but false one, and the zoölogist finds himself in the same predicament. How much weight should be allowed to a given likeness and how far it is offset by an accompanying difference, there are no certain means of determining, and we are still in search of those laws of organic change which shall render such service to zoölogy as Grimm’s law did to the study of the Indo-European languages. Doubtless, the analogy may be pushed still farther, and it may be confidently assumed that, just as sound principles of etymology were established by tracing the changes of words step by step from their modern forms to their ancient origins, so the existing animal forms must be traced back through the intermediate gradations to their distant ancestors, before the modes of organic development can be deduced from well-ascertained facts.

The evolutionary problem has been attacked by the aid of several distinct methods, each of which has its particular advantages and its peculiar limitations and drawbacks. Most of the methods suffer from the fact that they deal only with the present order of things, and thus resemble the attempt to work out the derivations of languages that have no literature to register their changes.

(1) Of necessity, the oldest of these methods is Comparative Anatomy, which had made great advances in pre-Darwinian days. It is the indispensable foundation of the whole inquiry, for an accurate knowledge of Comparative Anatomy is absolutely necessary to the use of the other methods; in the hands of the great masters it has registered many notable triumphs in determining the mutual relationships of animal groups; but finality cannot be reached by this method, because it deals only with existing forms and possesses no sure criterion for determining the value of similarities. It is thus unable to distinguish with certainty between those resemblances which are due to inheritance from a common ancestry and those which have been independently acquired. It is a very frequent fallacy to assume that, because two allied groups, B and C, possess a certain structure, their common ancestor, A, must also have possessed it. This may or may not have been the case, and Comparative Anatomy offers no assured means of deciding between those alternatives or of confidently distinguishing primitive characters from degenerative or retrograde changes.

(2) Embryology, which is the study of the development of the individual animal from the unfertilized egg to the adult condition, was long regarded as the infallible test of theoretical views in zoölogy. This was on the assumption that individual development (_ontogeny_) is a recapitulation in abbreviated form of the ancestral history (_phylogeny_) of the species, and was called by Haeckel “the fundamental biogenetic law.” It was soon learned, however, that the “recapitulation theory” was not to be implicitly trusted, for structural features which could not possibly be a part of ancestral history were imposed upon or substituted for those due to phylogenetic inheritance. Now the whole theory is strongly questioned, and the absence of any universally accepted rules of interpretation, by which the contradictory embryological data may be harmonized into a consistent whole, has deprived the method of that authoritative character once so generally ascribed to it. It is like dealing with a literature which has been vitiated with many forgeries, only the grossest of which can be readily detected. Embryology has rendered many great services in the solution of zoölogical problems and will no doubt render many more, but it cannot, of itself, reach final conclusions.

(3) Experimental Zoölogy, especially that part known as “Genetics,” one of the newest and most promising provinces of the science, has already taught us much concerning the laws of inheritance and the manner in which new characters arise, and no one can venture to fix the limits of its possible results. On the other hand, it does not seem likely that the larger problems of relationship and classification can be solved by this method, because of the brief time which the shortness of human life allows for the experiments.

(4) Palæontology suffers from the drawback that much of the past history of life is irretrievably lost, and even when the record is remarkably complete, as it is for certain chapters of the history, the material is but partially preserved. With such rare exceptions as are of little practical importance, only the hard parts, bones, teeth, etc., are retained and the soft parts completely destroyed. Nevertheless, Palæontology has the preëminent advantage of offering to the student the actual stages of development, and thus, to recur to the simile of language, has preserved original documents and in the true order of succession. It is true that it is well-nigh impossible to reconstruct a phylogenetic series of ancestor and descendant, unaffected by theoretical preconceptions, and the differences which arise in the interpretation of undisputed facts are caused by divergent beliefs concerning the actual course of the evolutionary process. If final and definitive results are ever to be reached, it must be through the coöperation of all the methods of research, and such results must be able to stand the tests applied by every sound method. On the other hand, the study of those phylogenetic series which are generally accepted as well established, should furnish us with some fairly definite information as to the modes in which development has operated in the past, since the order of succession in time fixes a limit to the rearrangement of related series. Some of the conclusions thus suggested may be stated here.

I. One of the most fundamental problems concerning the course of development is that which deals with _parallel_ and _convergent evolution_. The term _parallelism_ implies that forms having a common origin may independently run through a similar course of development and arrive at similar results. Illustrations of this principle are given by the many phyla of horses, rhinoceroses and camels, which persisted side by side through several geological stages, following independent, but parallel, courses of change. An even more striking case is that of the two subfamilies of the cats, the true felines and the †sabre-tooths. Whatever view may be taken of the relationships of these two groups, it is clear that, at least from the upper Oligocene to the Pleistocene, they were separate, but kept remarkably even pace with each other in their advance and specialization.

By _convergence_ is meant a similar result which is reached by two or more independent lines having different starting points, so that the descendants are more alike than were the ancestors, and is thus the opposite of _divergence_, the result of which is to make the descendants of common ancestors less and less alike with each succeeding stage. Either parallelism or convergence may be involved in the independent acquisition of similar characters, of which these are so many examples. It is obvious that this problem is fundamental and that little real progress is possible until a solution is reached. As to the correct solution, there is much difference of opinion among naturalists. Some deny altogether the reality and importance of these modes of development, but such are almost exclusively concerned with the modern world; others go to the opposite extreme, and looking upon every large group as polyphyletic, consider parallel and convergent development to be the rule of evolution. Few palæontologists are disposed to doubt that these modes of evolution are very frequent; their difficulty is to determine what limits can be drawn, and this difficulty can be removed only by much wider and more exact knowledge than we now possess.

So far as single structures are concerned, the fossils demonstrate unequivocally that they have been independently acquired in a great many cases. The resultant similarity may be attained through the loss, the acquisition or the modification of parts. The reduction of toes from the primitive number of five to four, three, two, or even one, has happened over and over again in the most diverse groups. There is good reason to believe that all the early and primitive placental mammals had the third trochanter on the femur and the epicondylar foramen on the humerus, but in most of the modern groups these structures are lost; and the list of such similar reductions of parts might be almost indefinitely extended.

Of much greater significance is the independent similar modification of parts and acquisition of new structures. Innumerable examples of this kind of parallel and convergent development might be given, but a few will be sufficient to illustrate the principle. (1) The odontoid process of the axis (second vertebra of the neck) was primitively a bluntly conical peg, a form which is still retained in the great majority of mammals, but in the true ruminants, the camels, the horses and the tapirs, the process is spout-shaped, concave on the upper side, convex on the lower. By tracing the development of those groups, it has been conclusively demonstrated that the change of form took place independently in each of the four. (2) The ruminants have molar teeth composed of four crescentic cusps arranged in two transverse pairs, the pattern called _selenodont_. The evidence is very strong that this highly characteristic molar pattern has been several times independently repeated, as in the true ruminants, the camels, the †oreodonts and probably other groups also. (3) The family †Macrauchenidæ of the extinct †Litopterna shares with the camel tribe the remarkable peculiarity of having the canal for the vertebral artery running through the neural arches of the neck-vertebræ. (4) A very striking instance is afforded by the three widely separated groups of hoofed animals, members of which had their hoofs transformed into claws; the †chalicotheres arose from the normal perissodactyls (p. 356), the †agriochœrids from the †oreodonts and the †Entelonychia from the †toxodonts. From time to time attempts have been made to unite two or more of these groups, but in each case better material and fuller knowledge have demonstrated the unnatural character of such association and the separate origin of the peculiar structure.

Admitting the reality and frequency of these modes of development, a far more difficult problem is to determine the extent to which such independent acquisition of similar structures has actually been carried, and it is at this point that the widest divergences of opinion are to be found. As yet, our knowledge is far too imperfect to permit the making of positive statements, but there is no evidence which would justify the conclusion that the same genus, family or order of mammals ever arose independently from radically different ancestors. We have no reason to believe that identical groups of mammals were ever separately developed in land areas which through long periods of time had no means of intercommunication. If such a thing ever happened, it must have been the rarest of exceptions. On the other hand, parallelism, by which _related_ forms pass through similar stages of development, would seem to have been so exceedingly common, as fairly to deserve being called a normal method of evolution. As more and better material has been gathered, it has grown increasingly clear that almost every large group of generic, family or higher rank, whose history is known in any adequate measure, consists of several distinct, though related phyla, which pursued more or less closely parallel courses of modification, though diverging from one another sufficiently to make the distinction of them comparatively easy. The parallelism was thus not exact, however perfect it may have been in particular structures, and the longer the phyla persisted, the more distinctly did they diverge.

A typical problem, which involves these principles, is afforded by the very curious and interesting group of South American hoofed animals known as the †Litopterna (Chap. XIII). The many remarkable resemblances between these ungulates and the perissodactyls and, more specifically, between the family †Proterotheriidæ and the horses, have been very differently interpreted by palæontologists. Some have insisted that the †Litopterna should be merged in the Perissodactyla, on the ground that such a degree of likeness could not have been independently acquired. Others hold that this is a remarkable case of parallelism or convergence, and the latter is, in my opinion, much the more probable view. Until the ancestry of both groups, Perissodactyla and †Litopterna, shall have been definitely ascertained, it will not be practicable to make a final decision between these alternatives, nor, if the similarities were really independently acquired, to determine whether parallel or convergent evolution is involved. It is quite possible that both groups were rooted in the common ground of the †Condylarthra, and, if so, their relation is one of parallelism; but no such common ancestry has been proved, and it is equally possible that their ancestry was totally distinct. In the latter case the resemblances were due to convergence.

Assuming that the remarkable resemblances between the †Proterotheriidæ and the horses were separately acquired, it should be emphasized that these similarities nowhere amount to identity. The likenesses are not confined to a few structures, but are general throughout the skeleton and may be noted in the teeth, skull, trunk, limbs and feet, but in every single one of these parts the similarities are offset by differences of great significance. No competent anatomist would mistake any of the bones of the †proterotheres for the corresponding parts of the horses, whatever view he might hold as to the relationship between the two groups. The case is thus one of a very instructive kind, as tending to show that identity of structure in so highly complex creatures as mammals is not independently attained by widely separated or entirely unrelated forms. Probable as this conclusion is made by all the available evidence, it cannot be regarded as demonstrated; it is proverbially impossible to prove a negative.

On the other hand, it is equally probable that nearly related forms do very frequently, perhaps normally, pass through separate, but closely similar, courses of development. It is likely that a new species is usually formed through similar and simultaneous modification of many individuals, rather than from a single individual or pair. It may be the general rule, as almost certainly has often happened, that a new genus arises by the separate assumption of the new character by several species of the ancestral genus, rather than through the rapid diversification of a single species, though, no doubt, parallel and divergent modification are both very frequent and important processes. Dr. Eigenmann concludes from his study of South American fresh-water fishes that a certain new genus is even now in process of origin through the transformation of several species of an older genus, which in different parts of the continent are simultaneously, but independently, taking on the new character.

Sometimes it is possible to assign a definite reason for the independent origin of similar structures in different groups of mammals. Except for the head, there is much similarity of appearance among the very massive hoofed animals, such as the elephants, rhinoceroses, tapirs and hippopotamuses of the present time, a fact which induced Cuvier to unite them in one order, the “Pachydermata,” a term which has passed into vernacular, if metaphorical, usage. No doubt also, several extinct groups, such as the †Amblypoda and the perissodactyl family of the †Titanotheriidæ, would have been included, had they been known in Cuvier’s day. In the largest and heaviest of these animals, the elephants, †amblypods and †titanotheres, there are many close correspondences in all parts of the skeleton, which are clearly due to the mechanical necessities imposed by the support of immense weight, and the developmental history of each group shows that the smaller and lighter ancestors were less similar than the larger and more massive descendants. Such subsequently acquired likenesses are thus obvious examples of convergence and were caused by adaptation to similar needs.

Fürbringer has shown that among birds size and weight of body determine many resemblances between unrelated families, the largest forms displaying a more advanced grade of specialization.

It is thus extremely probable that evolution is a highly complex process, in which divergent, parallel and convergent modes of development are normally concerned. This complexity greatly increases the difficulty of determining phylogenies, which would be very much easier could every notable resemblance be at once accepted as proof of relationship. It often renders impossible the classification of some isolated group, which seems to have several incompatible affinities. It emphasizes the necessity of founding schemes of classification upon the totality of structure and the importance of determining the value of characters, whether they are primitive or advanced, divergent, parallel or convergent, before attempting to use them in classification.

In looking over the field of mammalian evolution, so far as that is recorded by the fossils, the general impression received is that the most important process is divergent development, one line branching out into several. This process became especially vigorous and rapid at times of important change in the character of the environment, what Osborn has called “adaptive radiation.” As we have repeatedly observed in the history of particular groups, _e.g._ the rhinoceroses, horses and camels, numerous parallel phyla of the same family existed together in certain geological stages, but as these phyla were traced back in time, they were found to draw together and display themselves as branches of a single stem. This favours the inference that the mammalian orders, so far as they are truly natural groups and not arbitrary assemblages, are each of single, or monophyletic, origin, and that the parallel and convergent modes of development, while very frequent and important, are subordinate to divergence.

II. A second problem is whether development among mammals is always by means of reduction in the number of parts, or whether that number may not be increased. With this is involved the so-called law of the “irreversibility of evolution,” according to which organs once lost, or reduced to a vestigial condition, are never regained, or reëstablished in function. There can be no question that the usual mode of mammalian development is by reduction in the number of parts and the enlargement and elaboration of those which are retained, as, for example, in the reduction of five toes to one in the series of the horses; but there are cases which require a different explanation. The very numerous teeth of the porpoises and dolphins and of the Giant Armadillo are not a primitive feature, but must have arisen by a process of multiplication. In the very curious Large-eared Wolf (_Otocyon_) of South Africa the number of molar teeth 3/4 exceeds that found in any other placental mammal. This feature has been interpreted as a proof of marsupial relationship, but, as the creature is a typical dog in all other respects, such a relationship would involve a degree of convergence in development that is quite inadmissible without the most cogent evidence. Until something is learned regarding the descent of _Otocyon_, no positive statement can be made as to the significance of its exceptional dentition, but much the most likely supposition is that additional teeth have been developed in an otherwise normal canid. However that may be, the testimony of the fossils is unequivocally to the effect that the usual mode of development among mammals is by a reduction in the number of parts, accompanied by enlargement and specialization in those which are retained.

It is equally clear that the “law of irreversibility” holds good in a very large number of cases, but whether it is always valid is very doubtful. In the Guinea Pig, as in all its family (Caviidæ), there are four toes in the front foot, three in the hind; but Professor Castle has lately succeeded in producing a race with four toes in the hind foot. To call this a “monstrosity” or “abnormality” explains nothing; the fact remains that the four-toed race has been established and no reason can be assigned why the same thing might not happen in nature. If Dr. Matthew’s view concerning the origin of the American deer from _†Leptomeryx_ (p. 409), should prove to be well founded, another example of the same kind would be furnished. In _†Leptomeryx_ of the Oligocene the upper canine was reduced to minute, almost vestigial proportions, while in the ancestral deer, _†Blastomeryx_ of the lower Miocene, it was a large, scimitar-like tusk. While I am unable to accept this derivation of the deer, it may be true nevertheless and, if so, will be a most interesting example of the rehabilitation of a vestigial organ. Decision must await the discovery of the intermediate forms. Many such cases and instances of the addition of parts may be so far undetected, but the phylogenetic series, as we have them before us, point decidedly to the conclusion that such rehabilitation or new addition is exceptional.

III. So far as we are able to follow it by the aid of the fossils, development among the mammals would appear to be a remarkably direct and unswerving process. When any long-lived phylum, made up of numerous well-preserved members, is studied, the observer cannot fail to be impressed by the straightforward course of the evolutionary process, as though the animals were consciously making for a predetermined goal, which, needless to say, they were not. A minute cusp makes its appearance on a tooth, enlarges steadily in each succeeding genus, and ultimately becomes a very important element in the pattern; and in this series of changes there is no oscillation backward and forward. In the perissodactyls and a few other groups, the premolars in each family gradually and steadily assumed the size and complexity of molars; beginning at the hinder end of the series, these teeth one by one become molariform, not in irregular and haphazard fashion, but by perfectly graded stages. The same gradual and direct process was maintained in the oft-recurring reduction of digits among the hoofed animals, differing for each group according to the symmetry of the foot. In the horses, for example, the first digit became vestigial and disappeared, and then the fifth followed, leaving a three-toed foot, in which the median digit was notably the largest and bore most of the weight. Throughout the Oligocene and Miocene epochs the horses were all tridactyl, but there was a gradual enlargement of the median digit and dwindling of the laterals, until these became mere dew-claws, not touching the ground, and the weight was carried entirely upon the median one. Finally, the laterals lost their phalanges and were farther reduced to splints, which is the modern condition. In the same gradual and unswerving manner the higher artiodactyls went through a process of digital reduction from five to two, and numberless other instances of similar sort might be adduced.

On the other hand, the direction of change long followed may be departed from, the deviation being due to the introduction of a new factor. In the earliest deer the males were hornless, but they developed effective weapons of defence by the enlargement of the upper canine teeth into long and sharp, sabre-like tusks. When antlers appeared, the work of defence was transferred to them, and the tusks began to dwindle, being eventually suppressed in those deer which had large and complex antlers, though persisting to the present time in the hornless Musk Deer and in the small-antlered Muntjaks, which can defend themselves with their sharp tusks.

It would be inaccurate to say that fluctuations in the size and effectiveness of parts never occurred; on the contrary, there is evidence that such fluctuations in details were not infrequent, and may have been even more common than we suppose. To give one instance, the very early camels of the upper Eocene and lower Oligocene had small canines, which though not at all functionless or vestigial, were yet little larger than incisors. Though the ancestral camels of the middle and lower Eocene are not yet definitely known, there is strong reason to believe that in them, as in all of their contemporaries among the ungulates, the canines were enlarged and fang-like. If so, the canine teeth in the camels underwent decided fluctuations in size, being first larger, then smaller and again enlarging. If Dr. Matthew’s interesting theory as to the origin of the true felines from primitive †sabre-tooth cats (see p. 540) should be confirmed, it would furnish a very striking example of fluctuating development. The acceptance of the theory involves the admission of the following changes: (1) The upper canine was enlarged and changed into a thin, recurved, scimitar-like tusk; (2) the lower canine was much reduced, becoming little larger than the incisors; (3) the lower jaw developed a flange on each side from its inferior border, against which the inner side of the upper canine rested, when the mouth was closed, and the chin was nearly flat, meeting the outer surface of the jaw at a right angle. After these peculiarities had been fully established, the stock divided into two series; in one, the †machairodonts, the specialization continued along the same lines, assuming more and more exaggerated forms, while in the true cats it was reversed. The upper canine grew shorter and thicker, the lower canine was very greatly enlarged, the lower jaw lost its flange, and its external and anterior surfaces no longer met at a right angle, but curved gradually into each other. As previously stated, such a reversal strikes me as improbable and not to be accepted without very much more complete evidence than we now have, but it is perfectly possible that such evidence may be forthcoming.

Making the fullest allowance for all such cases of fluctuation, it remains true that in the great majority of the phyla whose history may be followed in some detail, development has been remarkably direct and unswerving. Plasticity of organization and capacity for differentiation of structure in widely different directions would seem to be limited in the mammals, especially among the more advanced groups.

IV. A question that has been much debated and is still a centre of controversy deals with continuity and discontinuity in development. In other words, does evolution proceed by the cumulative effects of minutely graded modifications, or is it a succession of leaps and sudden changes? The difference is illustrated by many breeds and races of animals and plants under domestication, the history of which is known. Some have arisen from “sports,” sudden and marked deviations from the parent stock, which “breed true” from the beginning. Of this character was the Ancon breed of sheep, which was derived from a single short-legged ram that was born of normal parents in 1791 and transmitted his peculiarities to his offspring. Professor Castle’s race of four-toed Guinea Pig originated from one four-toed individual, which suddenly appeared in a litter of normal ones. Other breeds have been formed by the careful and long-continued selection of minute individual variations. Which of these methods is the one that has been followed under natural conditions? or has now one method been used and now another, according to circumstances? The problem is one that has a profound and far-reaching importance for the whole of evolutionary philosophy, which largely hinges upon it.

Unfortunately, palæontology is not well fitted to give a decisive answer to these questions, for, however complete the record of any given series may be, we never can be sure that it actually is so, and interruptions in the continuity of development might be due either to progress by abrupt changes, or to a failure to preserve all the gradations. For that reason different observers have put divergent interpretations upon the facts as we have them. The general impression that is made by the study of a well-preserved mammalian phylum is that of continuity, but a closer analysis reveals numerous small breaks, and suggests, so far as the record may be trusted, that the advance was made by separate steps, though very short ones. Indeed, it has been objected that so completely recorded a phylum as that of the horses must be illusory, because there is not perfect continuity between the successive genera, it being taken for granted that such continuity is the normal mode of development.

Dr. Schlosser, on the other hand, is a disbeliever in perfect continuity. “I am of the opinion that we must reckon with development _per saltum_ more frequently than is usually done. We have been decidedly spoiled by the phylogenetic series of quiet successive development, such as we meet with in the Oligocene and Miocene of North America in the titanotheres, oreodonts, camels, etc., and in the upper Eocene of Europe in _Palæotherium_, _Paloplotherium_, etc., as well as from the Oligocene into the Pleistocene, _e.g._, in the rhinoceroses, cervids, suillines, amphicyonids. Even here we often make for ourselves artificial difficulties by balancing, with an exaggerated scrupulousness, the individual forms one against another, to see whether they really are exactly fitted to fill up any gaps. It is not the lack of suitable intermediate forms which so often renders difficult the establishment of genetic series, but, quite on the contrary, the abundance of the forms at our disposal, among which we must make a choice. If, however, the development of phyla did not take place in the same region and under constant climatic and topographical conditions, we must necessarily find apparent gaps, for adaptation to a new environment occasions rapid changes of organization, so that the immediate descendant will often deviate considerably from its ancestor. But that must not mislead us into denying the connection between such forms.”[22]

Better adapted to a solution of this problem than mammals are the fossil shells of Mollusca, the development of which may often be traced through a thick series of strata, each step of modification being represented by innumerable individuals. In very many instances it appears that each species in a series of successive modifications had many contemporary fluctuating variations, but the change from one species to the next succeeding one was by a small though abrupt mutation. The difference between two successive species may be no greater than that between two contemporary variants of the same species, but it was a constant and not a fluctuating difference. There is much reason to believe that such is at least a frequent mode of development, namely, that from species to species and genus to genus the transition has been by slight and sudden changes. The possibility that such abrupt changes, however slight, are illusory and due to small gaps in the record, must be admitted, and though this does not seem to be a very likely explanation, it is given plausibility by the almost perfect continuity between successive species which may sometimes be observed.

The extremely important and significant distinction between contemporary, fluctuating variations and successive, constant mutations was first drawn by Waagen, who says of them: “One must therefore distinguish strictly between varieties in space and those in time. To describe the former, the long-used name ‘variety’ will suffice, for the latter, on the other hand, I would propose, for the sake of brevity, a new term, ‘mutation.’ A species as such, with reference to its connection with earlier or later forms, may be conceived and regarded as a mutation. But also in regard to the value of these two concepts, just established (variety and mutation), an entirely different value is displayed on closer consideration. While the former appears extremely vacillating, of small systematic value, the latter, even though in minute characteristics, is extremely constant and always to be recognized with certainty.”[23]

The same conception was adopted and elaborated by Neumayr: “Still other characteristics appear, which mark mutations as something different from varieties, especially that, as a rule, there is a definite direction of mutation in each series, the same characters changing in the same sense through a considerable succession of strata.”[24]

Whether development was continuous or discontinuous, there is no reason to suppose that the amount and rate of modification were always constant. On the contrary, there is strong evidence that at times of great climatic or geographical changes, or when a region was invaded by a horde of immigrants, widespread readjustments were accomplished with comparative rapidity. Indeed, such periods of relatively quick changes have long seemed to be implied by the facts of the palæontological records.

* * * * *

It is only too clear that the principles as to the modes of mammalian development which can be deduced from the history of the various groups must, for the most part, be stated in a cautious and tentative manner, so as not to give an undue appearance of certainty to preliminary conclusions, which should be held as subject to revision with the advance of knowledge. Much has, however, been already learned, and there is every reason to hope that Experimental Zoölogy and Palæontology, by combining their resources, will eventually shed full light upon a subject of such exceptional difficulty.

FOOTNOTES

[1] Memoirs of the University of California, Vol. I, pp. 209-211.

[2] Voyage of a Naturalist, Amer. ed., pp. 133-134.

[3] J. W. Gregory, The Great Rift Valley, p. 268.

[4] Voyage of a Naturalist, Am. ed., 1891, p. 82.

[5] D. H. Scott, Studies in Fossil Botany, London, 1900, pp. 524-525.

[6] The names, Javan and Sumatran rhinoceroses, are somewhat misleading, since both of these species are also found on the mainland of India.

[7] This plausible and no doubt correct explanation was suggested to me by my colleague, Professor C. F. Brackett.

[8] Flower and Lydekker, Mammals Living and Extinct, p. 332.

[9] Flower and Lydekker, _op. cit._, pp. 307-308.

[10] Flower and Lydekker, _op. cit._, pp. 355 and 357.

[11] The Woodland Bison of Canada is now regarded as a distinct species.

[12] Darwin, Voyage of a Naturalist, p. 172.

[13] F. E. Beddard, Mammals, London, 1902, pp. 550, 551.

[14] Bates, Naturalist on the Amazons, London, 1875, pp. 32, 140.

[15] Bates, Naturalist on the Amazons, London, 1875, pp. 332, 333.

[16] Beddard, _op. cit._, pp. 555, 556.

[17] A. Hrdlička, Smithsonian Institution, Bureau of Ethnology, Bulletin 33, 1907, p. 98.

[18] _Ibid._, Bulletin 52, 1912, pp. 385, 386.

[19] K. von Zittel, Handbuch der Palaeontologie, Bd. IV, p. 132.

[20] Reports of the Princeton University Expeditions to Patagonia, Vol. IV, Pt. 3.

[21] W. K. Gregory, The Orders of Mammals; Bull. Amer. Mus. Nat. History, Vol. XXVII, p. 211.

[22] M. Schlosser, Beiträge zur Kenntniss der Oligozänen Landsäugethiere aus dem Fayum, Vienna, 1911, p. 165.

[23] W. Waagen, Die Formenreihe des Ammonites subradiatus, _Benecke’s Geognost.-Palæont. Beitr._, Bd. I, pp. 185-186.

[24] M. Neumayr, Die Stämme des Thierreiches, Bd. I, p. 60.

GLOSSARY

=Acetabulum=, the deep socket in the hip-bone for the head of the femur.

=Acromion=, the projecting lower end of the spine of the shoulder-blade.

=Alisphenoid canal=, canal in the base of the skull for the external carotid artery.

=†Allotheria=, an extinct suborder of Mesozoic and Paleocene Marsupials.

=†Amblypoda=, an extinct order of hoofed mammals.

=Anconeal fossa=, a deep pit on the posterior side of the humerus, near the lower end.

=Anconeal process=, _see_ Olecranon.

=†Ancylopoda=, an extinct suborder of Perissodactyla.

=Angle=, of the lower jaw, the postero-inferior corner.

=Angular process=, a hook-like projection from the angle of the lower jaw.

=Anterior nares=, the forward opening of the nasal passage.

=Anthropoidea=, Monkeys, Apes, Man; suborder of Primates.

=Appendicular skeleton=, bones of the limbs and limb-girdles.

=Araucanian=, Pliocene of Argentina, including the Catamarca and Monte Hermoso.

=Artiodactyl=, _see_ Artiodactyla.

=Artiodactyla=, Cattle, Deer, Camels, Pigs, etc., etc., order of hoofed mammals.

=Ascending ramus=, posterior, vertical portion of the lower jaw.

=Astragalus=, the ankle-bone.

=Astraponotus Beds=, upper Eocene or more probably, lower Oligocene of Patagonia.

=†Astrapotheria=, an extinct order of hoofed mammals.

=Atlas=, the first vertebra of the neck.

=Auditory bulla=, one of a pair of inflated bony capsules at the base of the skull; the tympanic bone.

=Auditory meatus=, the entrance to the bulla.

=Axial skeleton=, the skull, backbone, ribs and breast-bone.

=Axis=, the second vertebra of the neck.

=†Barytheria=, an extinct order of elephant-like mammals.

=Biceps muscle=, the large flexor muscle of the front of the upper arm; its contraction bends the elbow.

=Bicipital groove=, a groove between the tuberosities of the humerus for the upper tendons of the biceps.

=Brachyodont=, low-crowned teeth, with early-formed roots.

=Bridger stage=, middle Eocene of N. W. America.

=Bunodont=, teeth composed of conical tubercles.

=Calcaneum=, the heel-bone.

=Cannon-bone=, a compound bone formed by the coössification of two or more long bones of the foot.

=Cape Fairweather=, marine Pliocene of Patagonia.

=Carnassial=, a shearing, sectorial tooth in a flesh-eater.

=Carnivora=, Wolves, Bears, Cats, etc., etc.; an order of placental mammals.

=Carnivorous=, flesh-eating, predaceous.

=Carpal=, one of the elements of the carpus.

=Carpus=, the wrist-bones.

=Casa Mayor stage=, terrestrial formation of Patagonia, probably Eocene.

=Catamarca=, a Pliocene formation of Argentina.

=Caudal vertebræ=, those of the tail.

=Central=, a small carpal, wedged in between the two rows.

=Centrum=, the body of a vertebra.

=Cervical vertebræ=, those of the neck.

=Cetacea=, Whales, etc.; a cohort of marine mammals.

=Chelodactyla=, suborder of Perissodactyla.

=Chevron-bones=, Y-shaped bones attached to the under side of the caudal vertebræ.

=Chevrotains=, “Mouse Deer,” of the suborder Tragulina.

=Chiroptera=, Bats, an order of placental mammals.

=Class=, a group of the fifth order in classification.

=Clavicle=, the collar-bone.

=Cnemial crest=, a massive prominence on the front face of the tibia, near the upper end.

=Cohort=, division of infraclass, containing a series of related orders.

=†Condylarthra=, an extinct order of hoofed mammals.

=Condyle=, a knob-like, articular protuberance.

=Convergence=, or =Convergent Evolution=, similar forms resulting from two or more independent lines of descent.

=Coracoid=, a hook-like bone, fused with the shoulder-blade in the higher mammals.

=Coronoid process=, a projection in front of the condyle of the lower jaw, to which the temporal muscle is attached.

=Cotyles=, concavities on the atlas to receive the occipital condyles of the skull.

=Cranium=, the part of the skull above and behind the eyes, which lodges the brain and higher sense-organs.

=†Creodonta=, an extinct suborder of the Carnivora.

=Cretaceous=, third and last of the Mesozoic periods.

=Crown=, the exposed part of a tooth.

=Deltoid crest=, a ridge on the anterior face of the humerus for the attachment of the deltoid muscle.

=Dental formula=, an arithmetical expression of the number and kinds of teeth.

=Dermoptera=, Flying Lemur, order of placental mammals.

=Deseado stage=, terrestrial formation of Patagonia, probably Oligocene.

=Didelphia=, lower infraclass of the Eutheria.

=Digit=, a finger or toe.

=Diprotodonta=, Kangaroos, etc., a suborder of Marsupials.

=Dorsal vertebræ=, those which carry ribs.

=Duplicidentata=, Hares and Rabbits, suborder of Rodentia.

=Edentata=, Sloths, Anteaters, etc., an order of placental mammals.

=Edentates=, _see_ Edentata.

=†Embrithopoda=, an extinct order of elephant-like mammals.

=Embryo=, young animal in early stages of development within the uterus.

=†Entelonychia=, extinct suborder of the †Toxodontia.

=Eocene=, second of the five Tertiary epochs.

=Epicondylar foramen=, perforation of the internal epicondyle for transmission of the ulnar nerve.

=Epicondyle=, a rough prominence on each end of the humeral trochlea.

=Epiphysis=, the ends of the long bones, which ossify separately and do not coalesce with the shaft until growth ceases.

=Equus Beds=, _see_ Sheridan stage.

=Eutheria=, the higher subclass of mammals; viviparous.

=Family=, group of the third order in classification, typically containing several genera.

=Fauna=, the totality of animals of a given time or place.

=Femur=, the thigh-bone.

=Fibula=, the external bone of the lower leg.

=Fissipedia=, land-carnivores; suborder of the Carnivora.

=Flora=, the totality of plants of a given time or place.

=Fœtus=, young animal in the later stages of development within the uterus.

=Foramen=, a perforation in a bone for the passage of a nerve or blood-vessel.

=Foramen magnum=, the opening in the occiput for the passage of the spinal cord to the brain.

=Formation=, a general term for a group of strata, laid down continuously and under uniform conditions.

=Frontal=, one of a pair of bones which form the anterior part of the cranial roof; the forehead.

=Genus=, group of the second order in classification, typically containing several species.

=Glenoid cavity=, (of the squamosal) the articular surface for the condyle of the lower jaw; (of the scapula) the socket for the head of the humerus.

=Hallux=, the first digit of the pes, or great toe.

=Herbivorous=, plant-eating.

=†Homalodotheres=, _see_ †Entelonychia.

=Horizontal ramus=, the tooth-carrying part of the lower jaw.

=Humerus=, the bone of the upper arm.

=Hyoid arch=, a series of bony rods, attached to the base of the cranium, for support of the tongue.

=†Hyopsodonta=, an extinct suborder of the Insectivora.

=Hypsodont=, high-crowned teeth, with late-formed roots.

=Hyracoidea=, Klipdases, an order of hoofed mammals.

=Ilium=, the anterior element of the hip-bone.

=Inferior maxillary=, the lower jaw.

=Infraclass=, division of subclass.

=Insectivora=, Moles, Shrews, etc., an order of placental mammals.

=Ischium=, the postero-superior element of the hip-bone.

=John Day stage=, upper Oligocene of N. W. America.

=Jugal=, the cheek-bone. _See_ Malar.

=Jurassic=, the second of the Mesozoic periods.

=Lachrymal=, a small bone on the front edge of the orbit.

=Lachrymal foramen=, a canal for the tear-duct piercing the lachrymal bone.

=Lemuroidea=, Lemurs, suborder of the Primates.

=Lemurs=, _see_ Lemuroidea.

=Limb-girdles=, the bones which attach the limbs to the body.

=Lipotyphla=, suborder of the Insectivora.

=†Litopterna=, extinct order of hoofed mammals.

=Loricata=, Armadillos and Glyptodonts; the armoured Edentates.

=Lumbar vertebræ=, those of the loins.

=Lunar=, the middle bone in the upper row of the carpus.

=Magnum=, the middle bone in the lower row of the carpus; supports the third digit or middle finger.

=Malar=, cheek-bone. _See_ Jugal.

=Malleolar bone=, the lower end of the fibula, persisting as a separate bone after loss of the shaft.

=Malleolus, external=, the lower end of the fibula.

=Malleolus, internal=, process from the lower end of the tibia.

=Mammal=, a warm-blooded vertebrate, which suckles its young.

=Mandible=, the lower jaw.

=Manubrium=, the anterior segment of the breast-bone.

=Manus=, the hand or fore foot.

=Marsupial=, _see_ Marsupialia.

=Marsupialia=, Opossums, Kangaroos, etc., etc.; only order of the infraclass Didelphia.

=Marsupium=, the hairy pouch in which the young Marsupials are carried.

=Masseter muscle=, a muscle of mastication, attached to the lower jaw and inferior border of the zygomatic arch.

=Mastoid=, that part of the periotic bone which is exposed on the surface of the skull.

=Mastoid process=, a spine-like outgrowth of the mastoid.

=Maxillary=, the upper jaw-bone.

=Medullary cavity=, the marrow cavity of a long bone.

=Mesozoic=, the middle era of geological time.

=Metacarpal=, a member of the metacarpus.

=Metacarpus=, the long bones of the manus, or fore foot.

=Metapodial=, a metacarpal or metatarsal.

=Metatarsal=, a member of the metatarsus.

=Metatarsus=, the long bones of the pes, or hind foot.

=Miocene=, the fourth of the Tertiary epochs.

=Monodelphia=, placental mammals; the higher infraclass of the Eutheria.

=Monophyletic=, derived from a single line of ancestry.

=Monotremata=, Duck-billed Mole and Spiny Anteaters; the only existing order of the Prototheria.

=Monte Hermoso stage=, upper Pliocene of Argentina.

=Mouse Deer=, chevrotains; suborder Tragulina.

=Mystacoceti=, Whalebone Whales; order of the Cetacea.

=Nasal=, one of a pair of bones, forming the roof of the nasal passage.

=Navicular=, central bone of the tarsus.

=Neural arch=, the bony arch of a vertebra.

=Neural canal=, the cavity in the arch, lodging the spinal cord.

=Neural spine=, or spinous process, the projection arising from the summit of the neural arch.

=Notostylops Beds=, _see_ Casa Mayor stage.

=Occipital condyles=, a pair of knob-like protuberances from the occiput for articulation with the first vertebra.

=Occipital crest=, an elevated bony ridge around the margin of the occiput.

=Occiput=, the posterior surface of the skull.

=Odontoceti=, Toothed Whales; order of Cetacea.

=Odontoid process=, a peg-like projection from the body of the second vertebra, which fits into the ring of the first.

=Olecranon=, the heavy projection from the upper end of the ulna, forming the point of the elbow.

=Oligocene=, the third of the Tertiary epochs.

=Opposable=, used of the thumb and great toe, when they can be opposed to the other digits.

=Orbit=, the bony eye-socket.

=Order=, a group of the fourth rank in classification, typically including many families.

=Oviparous=, egg-laying.

=Palate, hard=, the bony roof of the mouth.

=Palatine=, one of a pair of bones which form the hinder part of the hard palate.

=Palatine process=, a shelf-like projection of the maxillary, which forms most of the hard palate on each side.

=Paleocene=, the oldest of the five Tertiary epochs.

=Palmate=, form of antler in which the tines are fused into large plates.

=Pampean=, Pleistocene, perhaps including the uppermost Pliocene, of Argentina.

=Parallelism=, or =Parallel Evolution=, similar development of related, but separate series.

=Paraná stage=, lower Pliocene (or perhaps upper Miocene) of Argentina.

=Parietal=, one of a pair of large, vaulted bones, which form most of the sides and roof of the cranium.

=Paroccipital process=, a bony projection from the infero-external angle of the occiput.

=Patagonian stage=, marine lower Miocene of Patagonia.

=Patella=, the knee-cap.

=Pecora=, true Ruminants, suborder of Artiodactyla.

=Pelvic girdle=, _see_ Pelvis.

=Pelvis=, the hip-bones.

=Periotic=, a small, dense bone, which lodges the internal labyrinth of the ear.

=Pes=, the hind foot.

=Petrosal=, _see_ Periotic.

=Phalanx=, one of the joints of the fingers or toes.

=Pholidota=, Pangolins or Scaly Anteaters; order of placental mammals.

=Phylum=, a genetic series of ancestors and descendants within a family.

=Pilosa=, Sloths, Anteaters, etc.; suborder of Edentata.

=Pinnipedia=, Marine Carnivores; suborder of Carnivora.

=Pisiform=, an accessory bone attached to the postero-external angle of the carpus.

=Placenta=, a temporary structure connecting mother and fœtus, by means of which the fœtus is nourished in the womb.

=Placental=, having a placenta; the Monodelphia.

=Pleistocene=, the older of the two Quaternary epochs.

=Pliocene=, the fifth and last of the Tertiary epochs.

=Pollex=, the first digit of the manus, or thumb.

=Polyphyletic=, derived from two or more distinct lines of ancestry.

=Polyprotodonta=, Opossums, etc.; suborder of Marsupials.

=Posterior nares=, the hinder opening of the nasal passage.

=Postglenoid process=, a bony ridge behind the glenoid cavity of the squamosal to prevent backward dislocation of the jaw.

=Postorbital process=, a bony projection from the frontal or jugal, bounding the eye-socket behind.

=Premaxillary=, the anterior bone of the upper jaw, carrying the incisor teeth.

=Primates=, Lemurs, Monkeys, Apes and Man; cohort and order of placental mammals.

=Proboscidea=, Elephants, etc.; order of hoofed mammals.

=Process=, a distinct prominence or projection of bone for the attachment of muscle or ligament.

=†Proglires=, an extinct suborder of the Insectivora.

=Prototheria=, most primitive subclass of mammals; oviparous.

=Pubis=, the postero-inferior element of the hip-bone.

=Pyramidal=, the external bone in the upper row of the carpus.

=†Pyrotheria=, an extinct suborder of †Toxodontia.

=Pyrotherium Beds=, _see_ Deseado stage.

=Radius=, the internal bone of the fore-arm.

=Rodent=, _see_ Rodentia.

=Rodentia=, Gnawers; order of placental mammals.

=Rotular groove=, a broad, shallow groove on the anterior face of the femur, near the lower end, in which the knee-cap glides.

=Round ligament=, the ligament between the head of the femur and a pit in the acetabulum of the hip-bone.

=Sacral vertebræ=, those of the sacrum.

=Sacrum=, a bony mass of fused vertebræ, for the support of the hip-bones.

=Sagittal crest=, a ridge of bone in the median line of the cranial roof, running forward from the occipital crest.

=Scaphoid=, the inner bone in the upper row of the carpus.

=Scapho-lunar=, a compound bone made up of the coalesced scaphoid, lunar and central.

=Scapula=, the shoulder-blade.

=Section=, primary division of a suborder.

=Sectorial=, a carnassial or shearing tooth of a flesh-eater.

=Selenodont=, teeth composed of crescent-shaped cusps.

=Shaft=, the body of a long bone, comprising most of its length.

=Sheridan stage=, older Pleistocene of the Great Plains.

=Shoulder-girdle=, the bones to which the fore limb is attached.

=Simplicidentata=, Squirrels, Rats, Porcupines, etc., etc.; suborder of Rodentia.

=Sinus=, an air-cavity in one of the skull-bones.

=Sirenia=, Sea Cows and Dugong; order of marine mammals.

=Species=, the unit group in classification, made up of individuals which are most closely similar.

=Spine=, (of the scapula) a bony ridge on the outside of the shoulder-blade; (of the tibia) a single or double prominence from the upper end of the shin-bone; (of a vertebra) the neural spine.

=Squamosal=, a bone forming the posterior side-wall of the cranium.

=Sternal ribs=, the inferior segments of the ribs, which articulate with the breast-bone.

=Sternum=, the breast-bone.

=Stratum=, a layer of bedded rock.

=Subclass=, primary division of class.

=Subfamily=, a group of related genera within the family.

=Subgenus=, a group of related species within the genus.

=Suborder=, primary division of order.

=Subspecies=, a definite subdivision of a species.

=Suina=, swine-like animals; suborder of Artiodactyla.

=Superfamily=, a group of related families.

=Superorder=, a group of related orders.

=Supinator ridge=, a crest on the outer side, near the lower end of the humerus, for attachment of the supinator muscle.

=Symphysis=, the line of junction of the two halves of the lower jaw.

=Synonym=, a name improperly given to a genus or species already named.

=†Tæniodontia=, an extinct order of clawed mammals.

=Tarsal=, an element of the tarsus.

=Tarsus=, the bones of the ankle-joint.

=Temporal muscle=, a muscle of mastication attached to the side of the cranium and the coronoid process of the lower jaw.

=Tertiary=, the more ancient of the two Cenozoic periods.

=Thoracic vertebræ=, _see_ Dorsal.

=Thorax=, the bony frame-work of the chest.

=Tibia=, the shin-bone, internal bone of the lower leg.

=†Tillodontia=, an extinct order of clawed mammals.

=†Toxodonta=, an extinct suborder of the †Toxodontia.

=†Toxodontia=, an extinct order of hoofed mammals.

=†Toxodonts=, _see_ †Toxodonta.

=Tragulina=, “Mouse Deer”; suborder of Artiodactyla.

=Transverse processes=, projections from the sides of a vertebra.

=Trapezium=, internal bone in the lower row of the carpus; supports the first digit, or thumb.

=Trapezoid=, second bone in the lower row of the carpus; supports the second digit, or index finger.

=Triassic=, first of the three Mesozoic periods.

=†Triconodonta=, an extinct suborder of Mesozoic Marsupials.

=†Trituberculata=, an extinct order of Mesozoic mammals.

=Trochanter=, a projection from the femur.

=Trochanter, third=, a hook-like process on the outer side of the shaft of the femur, near the middle of its length.

=Trochlea=, the pulley-shaped lower end of the humerus for articulation with the fore-arm bones.

=Trunk vertebræ=, those of the body, the dorsals and lumbars.

=Tubercle=, an articular projection on a rib, connecting with the transverse process of a dorsal vertebra.

=Tuberosities= (of the humerus), heavy projections from the upper end of the bone, in front of the head.

=Tubulidentata=, the Aard Vark; an order of placental mammals.

=Tylopoda=, Camels and Llamas; suborder of Artiodactyla.

=Tympanic=, a bone forming the support of the ear-drum and usually inflated into a hollow capsule.

=†Typotheres=, _see_ †Typotheria.

=†Typotheria=, an extinct suborder of the †Toxodontia.

=Ulna=, the external bone of the fore-arm.

=Unciform=, the external bone in the lower row of the carpus; supports the fourth and fifth digits, or ring and little fingers.

=Unconformity=, the relation between two groups of strata, one of which was deposited upon the worn surface or upturned edges of the other.

=Ungual phalanx=, the terminal joint of a digit, which supports the claw, nail or hoof.

=Unguiculata=, clawed mammals; cohort of Monodelphia.

=Ungulata=, hoofed mammals; cohort of Monodelphia.

=Ungulates=, _see_ Ungulata.

=Uterus=, the womb.

=Vagina=, the genital canal of the female.

=Variety=, a more or less constant group within a species.

=Vertebra=, a joint of the backbone.

=Vertebral column=, the backbone.

=Viviparous=, producing living young.

=†Zeuglodontia=, an extinct order of Cetacea.

=Zygapophyses=, the projecting processes, by means of which successive vertebræ are articulated together.

=Zygomatic arch=, a bony bridge from the eye-socket to the hinder part of the cranium.

INDEX

N. B.—The most important references are in =heavy-faced type=; technical names of genera and species are italicized, though most of the specific names are omitted as unnecessary. Extinct groups are indicated by a dagger (†).

Aard Vark, 60

_†Abderites_, 627, =641= (jaw fig.)

_†Achænodon_, 273, 361, 369 (skull fig.), =370=

†Achænodonts, Bridger, 369; Uinta, 369; Wasatch, 370

†Acœlodidæ, 477

Adaptive radiation, 655

_†Adinotherium_, 462, =473=, 474 (restoration)

_†Adpithecus_, 462

_†Ælurocyon_, 517, 551

_†Ælurodon_, 517, =527=

_Ælurus_, 546

Africa, 184, 245, 328, 332, 417, 419, 421, 422, 426, 442, 458, 481, 551, 579, 642, 656; elephants of, 138; mammals of, 145; zoölogy of, 146

AGASSIZ, L., 129

Age, geological, 15

Agouti, 185 (fig.)

_Agouti_, 183 (fig.), 185

Agoutis, Pleistocene, 218

†Agriochœridæ, 247, 250, 361, =383=, 484, 652; Eocene, 383; John Day, 250, 383; Oligocene, 383; Uinta, 267, 385; White River, 268, 383

†Agriochœrids, _see_ †Agriochœridæ

_†Agriochœrus_, 252 (restoration), 361, =383= (skull fig.), 384 (restoration), 385 (manus fig.)

Alachua stage, 127, 225

Alaska, 103, 106, 197, 199, 202, 203, 332, 418, 419, 420, 427, 433; †Mammoth in, 40; Miocene of, 118; Oligocene of, 113; Pleistocene glaciation in, 131; volcanoes, 133; Pliocene of, 125

_†Albertogaudrya_, 509, =512=

_Alce_, 65, 151, 156 (fig.), 202, 208, 362, 411, 412

ALLEN, J. A., 141, 161

Alligators, 102

†Allothere, Paleocene., 642 (skull fig.)

†Allotheria, 59, 627, =642=

_Alouatta_, 578, =585=

Alps, Arctic animals and plants of, 193; Eocene, 104

_†Alticamelus_, 224, 362, 388, =391=; restoration, 236

Amazon, 585; as barrier to species, 137

†Amblypoda, 60, =443=, 508; Bridger, 269, 445; Eocene, 443; Puerco, 286, 454; Torrejon, 285, 453; Wasatch, 277, 452; Wind River, 274, 450, 452

_†Amblytatus_, 592

AMEGHINO, F., 228, 263, 467, 471, 476, 496, 497, 613

America, connections of North and South, 123

American †Mastodon, 196; restoration, 195

Americas, marsupials of, 138

Amherst expedition, 487

Amphibia, 55; as ancestral to mammals, 643

_†Amphicyon_, 517, 524, =525=, 530

†Amphicyons, 558

_†Amphidolops_, 627

_†Amphiproviverra_, 627, =637=; skull fig., 637

_†Amynodon_, 272, 291, 340, =348=, 349

†Amynodontinæ, 291, 340, 341, =346=, 350, 351, 353; Bridger, 272, 350; Oligocene, 339; Uinta, 266, 348; White River, 255, 346.

†Amynodonts, _see_ †Amynodontinæ

_†Anacodon_, 277, 554, =561=

_†Analcitherium_, 592

†Anaptomorphidæ, 578, 583

_†Anaptomorphus_, 281, 578, =581=; head restored, 581

_†Anchitherium_, 290, 299

Ancon sheep, 660

†Ancylopoda, 60, 291, =353=; Bridger, 357; Miocene, 238, 355; Pliocene, 224, 355

Andes, 178, 179, 180, 185, 189, 211, 213, 322, 548; Eocene, 112; Miocene, 124; Pleist. glaciation, 133, 134; Plioc. 128, 129

ANDREWS, C. W., 422, 435

Antarctic continent, 103, 123, 638

Ant-Bear, 91, 187, 188 (fig.), 206, 591, 355, 600, 601, 615

Anteater, Collared, 187, 188 (fig.); Lesser, 591; tree, 591; Two-toed, 188

Anteaters, 60, 75, 94, 187, 189, 591, 593, 596; Pleistocene, 218, 596; Santa Cruz, 245, 596; scaly, 60, 353; spiny, 57, 59

Antelope, 202; bones of, 35; Mioc. restored, 237; Prong-horned, 5, 162 (fig.)

Antelopes, 54, 60, 222, 312, 362, 409, =416=, 418; flat-horned, 417; goat-horned, 417; Miocene, 235, 417; Old World, 202; Pleistocene, 202; Pliocene, 224; S. Amer., 213, 215, 221, 418, 466; strepsicerine, 225, 417; Tertiary, 419; twisted-horned, 417

†Anthracotheres, _see_ †Anthracotheriidæ

†Anthracotheriidæ, 259, 266, 361, =370=, 381, 384, 386

_†Anthracotherium_, 259, 361, 371

Anthropoidea, 60, 578, 579, 580, =582=

Anthropoids, _see_ Anthropoidea

Antigua, 134

Antilles, Eocene, 112; Miocene, 123; Oligocene, 117; Pliocene, 128

Antillia, 112; Oligocene, 117

_Antilocapra_, 162 (fig.), 202, 225, 362, =416=, 417

Antilocapridæ, 362, =416=

Antilopidæ, 416

Antler, 411

Antwerp, 37

Apar, 592

Apes, 60, 577, 578, 582, 583; night, 585

_†Aphelops_, 291

_Aplodontia_, 153, 233 (_see_ Sewellel)

Aplodontiidæ, 249

Appalachian Mts., 101, 150, 153

Aquatic habits, 2

Araucanian stage, 128

Arboreal animals, 2, 77, 84

Archæan period, 15

_†Archælurus_, 249, 517, 541, 543

†Archæohyracidæ, 462

_†Archæohyrax_, 462

†Archæopithecidæ, 462, 477

_†Archæotherium_, 259, 361, =367=; manus fig., 367; restoration, 252, =260=; skull fig., 367; teeth fig., 368

Arctic, archipelago, 125; islands, 210; fauna in Pleisto., 128; mammals, 109; regions, 128; Cretac. climate of, 26; Sea, 106; shells, Pleisto., 27; species, distribution of, 141; zone, 147 (map), 148

†Arctocyonidæ, 554, 557, =561=, 575; Torrejon, 285; Wasatch, 561

_†Arctotherium_, 211, 517, =549=, 553; head restor., 549

Argentina, 180, 185, 211, 213, 215, 218, 219, 245, 324, 391, 418, 436, 463, 466, 531, 586, 596, 597; drought in, 33; plains of, 133; Pliocene of, 20, 128; spread of horses and cattle in, 142

_†Argyrohippus_, 476

Arid province, 164

Aridity, evidences of, 24

Arikaree age, or stage, 17, =120=, 235, 259, 356

Armadillo, 5, 162, 591; 6-Banded, 189 (fig.), 592; 7-Banded, 592; 9-Banded, 190 (fig.), 592, 593; 11-Banded, 592; Bridger, 268, =616=; Giant, 190, 592, 612, 656; Pygmy, 592; restoration of Santa Cruz, 243, =480=

Armadillos, 60, 97, 141, 185, 189, 592, 593, 594, 595, =610=, 623, 624, 625; Araucanian, 226; Casa Mayor, 282, 595; Deseado, 262, 595, 616; Paraná, 228; Pleistocene, 218, 596, 612, 613; Santa Cruz, 245, 596, 612. (_See also_ Dasypoda _and_ Dasypodidæ)

Artiodactyl, †primitive, restoration, 252

Artiodactyla, 54, 55, 60, 69, 247, 284, 310, 355, =358=, 402, 459, 460, 491, 507, 514; Araucanian, 226, 227; Blanco, 222; Bridger, 273; classification, 361; John Day, 250; Miocene, 231, 235, 239; Neotropical, 176; North American, 176; Old World, 176, 362; Pleisto. N. Amer., 201; S. Amer., 213; Pliocene, 224; †Primitiva, 60, 361, =370=; Uinta, 266; Wasatch, 281; White River, 255, 257; Wind River, 275

Ash, volcanic, 29

Asia, 106, 239, 254, 258, 280, 317, 321, 328, 332, 352, 355, 369, 386, 390, 408, 413, 414, 417, 418, 419, 422, 426, 546, 550, 552, 579, 644; circumpolar area, 148; elephants of, 138; hyracoids of, 138; Minor, 458; Pleisto. glaciation of, 130; zoölogy of, 146

_†Asmodeus_, 462

Asphalt, 31

Ass, 52

Asses, 213, 292, 308

_†Asterostemma_, 592, 623

Astragalus, 88

_†Astraponotus_, 509, 512; Beds, 20, =281=, 282, 476, 479, 487

†Astrapothere, Santa Cruz, restoration of head, 243

†Astrapotheres, _see_ †Astrapotheria

†Astrapotheria, 60, 489, =508=, 514; of _†Astraponotus_ Beds, 282; Casa Mayor, 283, 512; Deseado, 264, 512; Patagonian, 512; Santa Cruz, 247, 508

_†Astrapothericulus_, 509, =512=

†Astrapotheriidæ, 509

_†Astrapotherium_, 243 (restor. of head), =509=, 510 (restor. of head)

_Ateles_, 578, =584=

Atlantic coast, Eocene, 104, 111, 117; Miocene, 117, 120; Oligocene, 113, 116; Paleocene, 101; Pliocene, 125; Tertiary mammals of, 369

Atlantic Ocean, 106, 109; connection with Pacific, 104

Atlas, 70 (fig.)

Auditory bulla, 66

Australia, 14, 21, 57, 58, 138, 140, 307, 340, 426, 461, 520, 550, 634; marsupials of, 626; Miocene, 123; Permian glaciation, 25; Pleistocene, 632, 634; rabbits introduced, 142; zoölogical peculiarity of, 145

Australian region, 640

Axis, 71 (fig.)

_Axis_, 46, 412

AZARA, 34

Baboons, 577, 582

Bad Lands, 107 (fig.)

Badger, 153, 162, 163, 168 (fig.), 517

Badgers, 174, 213, 518, 550, 551, 552; Pleistocene, 203, 204, 205

Bahia Blanca, 129

Bandicoots, 626

Barriers to spread of mammals, 139

†Barytheria, 60

Basal Eocene, 99

_Bassariscus_, 517, 546, 547

Bat, 89

BATES, H. W., 585

_†Bathyopsis_, 275, 443, =450=, 451, 455

Bats, 59; absence from Amer. Tertiary, 39; in European Tertiary, 39; West Indian, 191

Bear, Alaska Brown, 156 (fig.); African, 548; Black, 90 (pes fig.), 548 (teeth fig.); Pampean, 622; Polar, 148 (fig.), 548; †Short-faced, 549 (restor. of head); South American, 552; Spectacled, 172 (fig.), 176, 517, 548

†Bear-dog, 222; Miocene, 525 (restoration); primitive, 523 (skull fig.)

†Bear-dogs, 523, =524=, 530, 554, 558; John Day, 249; Oligocene, 526; Pliocene, 222; Pleistocene, 524

Bears, 4, 59, 90, 152, 163, 517, 518, 519, =548=, 553, 554; Old World, 204; Old World origin of, 518, 549; Paraná, 227; Pleistocene, 203, 204, 549; Pliocene, 223; polar, 141; †Short-faced, 210, 211, 517, =549=; true, 211, 527, 549. (_See also_ Ursidæ)

Beast, 1

Beasts of prey, 59, 92

Beaver, 2, 44, 157 (fig.); dentition, 96 (fig.); †Giant, 195 (restoration), =205=, 311, 222

Beaver Creek, Wyo., 12 (fig.)

Beavers, 60, 95, 153, 182; John Day, 249; Miocene, 238; Pliocene, 222; White River, 254

BEDDARD, F. E., 580, 587

Bedded rocks, 6

Bering, Sea, 100, 101; Strait, 197, 588; opening and closing of, 23; Pliocene, 125

BERRIDGE, W. L., 160, 171, 174, 175, 181, 183, 184, 185, 189, 320, 584, 633

Bicuspids, 93

Big Horn Basin, 107, 108, 109

Bighorn, 419

Binomial system of nomenclature, 42

Biogenetic law, 648

Birds, 655; distribution of, 141; migrations of, 143; Santa Cruz, 244

Bison, 4, 152, 162, 358; American, 154 (fig.); entombment of, 36; European, 152, 154 (fig.); Wood, 162, 419

_Bison_, 202, 362, =420=; _B. bison_, 152, 154 (fig.), =419=; _B. bonasus_, 152, 154 (fig.), 420; _B. †crassicornis_, 203, 420; _B. †latifrons_, 203, 420; _B. †occidentalis_, 589

Bisons, 409, 416, 418, =419=

Blanco age and stage, 17, =127=, 221, 388, 413, 551

_Blarina_, 163, 173

_Blastoceros_, 180 (fig.)

_†Blastomeryx_, 224, 241, 362, =414= (restoration), 657

Boar, Wild, 45 (fig. of sow and young), 46, 363

Bogs, burial of mammals in, 33

Bolivia, 178, 184, 215, 225, 436; Pleistocene, 20, 211; Pliocene, 129

Bones, gnawed, 36; Pleistocene, 40; preservation of, 36; Tertiary, 40

_†Boöchœrus_, 361, 367

Boreal, fauna, 178; region, 150; subregion, 150; zone, 147, 148 (map), 162, 164, 551, 588

_†Borhyæna_, 244, 494 (restoration), 627, =635=, 637 (skull fig.)

Borneo, 137, 327

_†Borophagus_, 517, 524, 530

_Bos_, 70

_†Bothriodon_, 252 (restoration), 259, 361, =370=, 371 (restoration)

Bovidæ, 362, =418=

†Bow-Tooth, 463

Brachyodont teeth, 95

_†Brachypsalis_, 517

BRACKETT, C. F., 368

_Bradypus_, 186 (fig.), 187, 591

Brain-casts, fossil, 41

Brazil, 118, 181, 190, 201, 213, 215, 218, 219, 221, 245, 324, 391, 436, 527, 530, 552; caverns of, 19, 30, 133, 211, 218, 221, 586, 596; Miocene, 596; Pleistocene, 20

Brazilian subregion, 164, 170 (map), 191

Bridger age and stage, 17, 30, 109, =110=, 340, 380, 386, 568; restorations of mammals, 271

British Columbia, Miocene, 118; Oligocene, 113; Pleistocene glaciation, 131; Pliocene, 125

Brocket, Wood, 181 (fig.)

Brockets, 181

BROWN, B., 210

Brown-tailed Moth, 143

_Budorcas_, 418

Buffalo, 36, 152

Buffaloes, 409, 416

Bulgaria, 316

_†Bunælurus_, 517, =551=

Bunodont teeth, 360

_†Bunomeryx_, 361

Buno-selenodont teeth, 371

Buried valleys, 132

BURMEISTER, H., 496, 497

Burrowers, 45, 79

Burrowing mammals, 77

Bush-Dog, 174, 212, 527, 530, 552

_Cabassous_, 592, 614, 616

_Cacajao_, 578, =585=

Cacomistle, 162, 517, 546

_Cænolestes_, 58, 190, 284, 626, =640= (skull fig.), 641, 642

Cænolestidæ, 627

_†Cænopus_, 238, 252 (restoration), 256 (do.), 291, 333, =336= (molar and skull fig.), 339 (front teeth fig.), 342, 351

_†Calamodon_, 274

Calcaneum, 88

California, Eocene, 104, 111; marine Pleisto., 132; Mesozoic, 23; Miocene, 118, 121, 127; Pliocene, 125

_Callithrix_, 218

_Caluromys_, 631

Cambrian period, 15; glaciation in, 25

Camel, 48, 54, 60, 70, 79, 358, 490; distribution, 138; family, 178; Miocene, 232 (restoration); tribe, 13; True, 178; White River, 252 (restor.)

Camelidæ, 362, =386=; distribution, 138

Camel-like animals, 386

Camels, 56, 81, 84, 87, 90, 257, 258, 312, 362, 373, =386=, 421, 461, 651, 655; Bridger, 273, 398; browsing, 388, 393; Eocene, 397, 398, 402, 659; grazing, 393; John Day, 250, 394; Miocene, 231, 232, 235, 241, 391; Old World, 231; Oligocene, 394, 402, 659; phyla of, 650; Pleistocene, 196, 202; Pliocene, 224, 388; true, 13, 386, 387, 390, 391; Uinta, 267, 397; White River, 257, 394

_Camelus_, 70, 138, 362, 387

Canada, 257, 357, 565; Eocene climate, 111; Paleocene, 102; White River, 113; zoölogy, 146

Canadian fauna, 151; subregion, 147, =150=

Canidæ, 173, 223, 517, 518, =520=; fox-like, 529 (_See also_ Dogs)

_†Canimartes_, 517

Canine teeth, 93

_Canis_, 152, 517, 522, 529; _C. †dirus_, restor., frontispiece, 204, 521; _C. †indianensis_, 204; _C. latrans_, 162, 165 (fig.), 632; _C. nubilis_, 159 (fig.); _C. occidentalis_, 62 (skull fig.), 64 (skull fig.), 162. (_See_ Wolves)

Cannon-bone, 84, 91 (fig.), 410 (fig.)

Cape Fairweather stage, 128

_†Capromeryx_, 362, 417

_Capromys_, 184

Capybara, 205. (_See also_ Carpincho _and_ Water Hog)

Capybaras, Pleistocene, 218

Carboniferous period, 15

Caribbean, region, Miocene, 123; Sea, Oligocene, 113

Caribou, 4, 181, 202, 207, 208, 210, 412, 413; Barren-ground, 148; Pleistocene, 27, 413; Woodland, 152, 157 (fig.)

Carnivora, 43, 59, 83, 90, 244, 268, 282, 284, 285, 459, =516=, 634; Araucanian, 226; Blanco, 222; Boreal, 152; distribution, 138; Eocene, 554; John Day, 249, 528; marine, 59; migration to S. Amer., 508, 518; Miocene, 229, 233, 238; Neotropical, 173; Pleistocene, N. Amer., 203, 210; S. Amer., 211; Plioc., 222; Sonoran, 163; Uinta, 265; White River, 254, 312

Carnivores, _see_ Carnivora

_†Carolozittellia_, 462, =488=

Carpincho, 183 (fig.), 185. (_See also_ Capybara _and_ Water Hog)

Carpus, 82

Casa Mayor age and stage, 20, =112=, 281, 488, 499, 512

Cascade Mts., 121; Oligocene craters of, 116

CASTLE, W. E., 657, 660

_Castor_, 96, 153, 157 (fig.)

_†Castoroides_, 195, =205=

Cat, 222; Domestic, 546 (manus fig.)

Catamarca age and stage, 20, =129=, 226

Catarrhina, 583, 587, 588

Cats, 54, 59, 90, 176, 517, 518, 519, =530=, 532, 553, 568; cursorial, 543; Miocene, 545; Native, 634, 638, 640; Oligocene, 530; Pleistocene, 545; Pleisto. S. Amer., 211, 212; Pliocene, 223, 545; South America, 552; true, 249, 517, 530, =543=. (_See_ Felidæ)

Cattle, 95; spread of, 142

Caves as sources of fossil mammals, 30

_Cavia_, 183 (fig.), 185

Cavicornia, 328, 411, 412, =416=, 421

Cavies, _see_ Caviidæ

Caviidæ, 185, 657; Araucanian, 226; Pleistocene, 218; Santa Cruz, 245

Cavy, Rock, 183 (fig.)

Caxomistle, _see_ Cacomistle

Cebidæ, 172, 578, =584=, 585

_Cebus_, 218, 578, =584= (fig.), 585

Celebes, 579

Cement, 96

Cenozoic era, 15, 16, 17, =18=, 99; South America, 19

_Centetes_, 173

Central, 83

Central America, 123, 164, 178, 179, 320, 585; Eocene, 104, 112; geology, 120; mammals, 141; Oligocene, 113, =117=; Paleocene, 103; tapirs, 137; Tertiary, 22; zoölogy, 146

Central American subregion, 164, 170 (map), =191=

_Cerdocyon_, 171 (fig.), 174, 517, 552

_†Cervalces_, 195 (restoration), 208, 209 (restoration), 362, =413=

Cervicornia, =411=, 421

Cervidæ, 362, =411=, 661; Neotropical, 179. (_See also_ Deer)

_Cervulus_, 412

_Cervus_, 208, 362; _C. canadensis_, 151, 155 (fig.), 202, 208, 411, 412; _C. elaphus_, 151; _C. eustephanus_, 151. (_See_ Deer)

Cetacea, 60, 442; Miocene, 123, 125

_Chætomys_, 184

†Chalicothere, 240 (restoration), 356 (manus fig.)

†Chalicotheres, _see_ †Chalicotheriidæ

†Chalicotheriidæ, 60, 247, 291, =354=, 383, 385, 458, 484, 651; Bridger, 357; John Day, 250, 357; Miocene, 231, 235, 238, 356; White River, 257, 357

_†Chalicotherium_, 354

CHAMBERLIN, T. C., 130

Chamois group, 202, 417; subfamily, 152

_†Champsosaurus_, 102

Cheeta, 542, 543

Chelodactyla, 60, 290

Chevron-bones, 73

Chevrotains, 54, 60, 408 (_see also_ Mouse-Deer _and_ Tragulina)

Chili, 124, 184, 436; marine rocks, 112; Pleistocene, 20; Pleisto. glaciation, 133

Chilian subregion, =164=, 170 (map)

_Chinchilla_, 184 (fig.), 185

Chinchilla-family, Araucanian, 226

Chinchillas, 185; Santa Cruz, 245

Chipmunks, 141, 153

_Chironectes_, 626, 627

Chiroptera, 59

_Chlamydophorus_, 190, 592

_†Chlamydotherium_, 218, 592, 596, 612, 614

_Cholœpus_, 74, 187 (fig.), 591

Chronology, geological, 10; of rocks, 6

Civet cats, 518, 558 (_see_ Viverridæ)

_†Cladoclinus_, 627

_†Cladosictis_, 243 (restoration), 627, =638=, 639 (restoration)

_†Clænodon_, 554, =561=

Classification of mammals, 50

Clavicle, 77 (fig.)

Clawed mammals, 59, 74, 456, 459, 460, 492, 514

Climate, as barrier to species, 140; determining distribution, 24; Cretaceous, 26; Eocene, 109, 448; Miocene, 122; Mioc. of Patagonia, 124, 244, 586; Oligocene, 116; Paleocene, 102; Pleistocene, 116, 134, 192; Pliocene, 127; vicissitudes of, 100

Climatic changes, 14; affecting distribution, 140; evidences of, 24; Pleisto., effects on migrations, 207

Coast Range, elevation, 122; Miocene, 113, 125

Coati, 162

Coatis, 76, 213, 517, 546, 552

_†Cochlops_, 592

_Coendou_, 182 (fig.), 184

_†Colodon_, 257, 291, =327=

Colombia, 626, 640

_†Colonoceras_, 272, 291, =347=, 350

Colouration, animal, 45

_†Colpodon_, 462

Columbia River valley, Miocene, 118

Comparative Anatomy, 647

Conard Fissure, 30, =210=

†Condylarth, 278 (restoration), 457 (skeleton fig.), 459 (restoration)

†Condylarthra, 60, 443, =456=, 484, 492, 499, 508, 514, 515, 653; Puerco, 286, 460; Torrejon, 285, 459; Wasatch, 277, 457; Wind River, 274, 456

_Condylura_, 152

_Conepatus_, 174 (fig.), 213, 517, 552

Conies, 60, 458, 481

Conifers, 103

Continental deposits, Eocene, 106, 112; Miocene, 120; Oligocene, 113, 117; Paleocene, 101; Pliocene, 127, 128

Continental islands, 140

Continuity of development, 660

Convergence, 650, 653, 655, 656

COPE, E. D., 306, 343, 399, 400, 401

Coracoid, 76

_†Coryphodon_, 275, 277, 279 (restoration), 285, 443, =452=, 454, 456

†Coryphodontidæ, 285, 443, 454; lower Eocene, 456

†Coryphodonts, _see_ †Coryphodontidæ

Costa Rica, 181; Pliocene, 128

Cotton-rats, 163

Coyote, 162, 165 (fig.)

Coyotes, Pleistocene, 218

_†Cramauchenia_, 489

†Creodont, 252 (restoration), 563 (restoration)

†Creodonta, 59, 516, 519, 527, 529, =554=, 574; Bridger, 268, 271 (restoration); Eocene, 633; Paleocene, 633; Puerco, 286; Torrejon, 285; Uinta, 265; Wasatch, 276; White River, 253; Wind River, 274. (_See_ Flesh-eaters)

Cretaceous period, 15, 16, 103, 112, 117, 261, 281, 443, 460, 514, 642, 643; climate, 26

Crocodiles, 122, 244; absent from John Day, 116; Eocene, 111; Paleocene, 284; White River, 116

Crown of tooth, 95

Crustal movements, Miocene, 122

_Ctenomys_, 184

Cuba, 173, 185; junction with Central America, 128, 598; Miocene, 123; Pleistocene, 134, 604; Pliocene, 128, 605

Cuboid, 89

Culebra Cut, Tertiary rocks, 22

Cuneiform, 83, 89

CUVIER, G., 44, 654

_Cyclopes_, 591

_†Cyclopidius_, 361, =376=

_†Cynodesmus_, 517, =522= (skull fig.), 523, 530

_†Cynodictis_, 254, 517, 529 (restoration), =530=, 547

_Cyon_, 213, 517, 527

_†Cyonasua_, 517

_Dama_, 412

_†Daphœnodon_, 517, =525= (restoration), 526, 530

_†Daphœnus_, 254, 517, 523 (skull fig.), 524 (manus and teeth fig.), =526=, 528, 530, 537, 546

DARWIN, C., 33, 35, 52, 136, 137, 143, 193, 217, 463, 489, 490, 491, 492

Dasypoda, 189, 592, =610=. (_See also_ Armadillos)

Dasypodidæ, 592

_Dasyprocta_, 185 (fig.)

_Dasypus_, 189 (fig.), 592, 611, 614, 616

Dasyures, Australian, 638

Dasyuridæ, 632, =634=, 640

Deep River age and stage, 17, =121=, 233

Deer, 46, 54, 60, 95 (molar fig.), 222, 312, 319, 360 (molar fig.), 362, 409, =411=, 461; American, 153, 162, 202, 208, 409, 412, 414, 420, 657; Axis, 412; Barking, 412; Black-tailed, 5, 202; Chinese Water-, 412; earliest, 658; Fallow, 412; Florida, 179 (fig.); Hog, 412; hornless, 414; Marsh, 179, 180 (fig.); Miocene, 232, 235, 414 (restoration); Mule, 46 (fawns fig.), 167 (fig.); Musk-, 224, 412, 658; Neotropical, 179; North American, 179; Old World, 151, 179, 181, 202, 412, 415; Pampas, 180; Patagonian, 91 (pes fig.), 410 (manus and pes fig.); Pleistocene, 202, 208, 412; Pleisto., S. Amer., 213, 215; Pliocene, 224, 226; South American, 415, 418, 466; southern, 412, 413; Tertiary, 412, 419; Virginia, 4, 166 (fig.), 179, 202, 412

†Deer-Antelopes, 202, =224=, 362, 417; Miocene, 232, 235, 414, 415 (restoration); Pleistocene, 417

Degu, 184

_†Deltatherium_, 554

Dental formula, 93

Dentine, 96

Deposits, continental (_see_ Continental deposits); lake, 37; river, 36

Dermoptera, 59

Deseado age and stage, 20, =117=, 282, 283, 474, 475, 477, 479, 481, 485, 486, 487, 508, 511, 512, 586, 587

Desiccation, Miocene and Pliocene, 128

_†Desmathyus_, 361

_†Desmatippus_, 290

_†Deuterotherium_, 489

Development, convergent, 446, 499; parallel, 499; per saltum, 661. (_See also_ Evolution)

Devonian period, 15; glaciation in, 25

Dhole, 213, 249, 517, 527, 530

_†Diadiaphorus_, 248, 489, 501 (skull fig.), 502 (restoration), =503= (pes fig.), 505, 507, 508

†Diceratheres, _see_ _†Diceratherium_

_†Diceratherium_, 238, 239 (restoration), 250, 256, 291, 333, 334, 350, 444

_Dicerorhinus_, 327, 329

†Dichobunidæ, 361, 398

Didelphia, =57=, 59, 626

Didelphiidæ, 627, =630=

_Didelphis_, 161, 626, 627, 631; _D. marsupialis_, 161 (fig.), 631

†Didolodidæ, 489

_†Didolodus_, 489

_†Didymictis_, 555, 558

Digit, 90

Digital reduction, 658

Digitigrade, 90

_†Dinictis_, 254, 517, =538=, 539 (restoration), 541 (pes fig.), 542, 546

†Dinocerata, 443

_†Dinocynops_, 517

_†Dinocyon_, 524

_†Dinohyus_, 239, 361, =366=

†Dinosaurs, 103, 284

†Dinotheres, _see_ _†Dinotherium_

_†Dinotherium_, 435, 438, 486

_†Diplacodon_, 266, 291, =313=, 317 (head restored)

_Dipodomys_, 163 (fig.)

Diprotodonta, 59, 627, =640=; Deseado, 642; Paraná, 641; Pleistocene, 641; Pliocene, 641; Santa Cruz, 640, 641; South American, 640

Discontinuity of development, 660

Dispersal of species, 143

_†Dissacus_, 554, =560=

Distribution, discontinuous, 127, 138, 193; geographical, of mammals, 135

Divergence, _see_ Evolution

_†Dœdicurus_, 212 (restoration), 219, =618=, 619 (restoration)

Dog, 90, 553; family, 558; fox-like, 529 (restoration)

Dogs, 90, 173, 517, 519, =520=, 548, 553, 554, 558; Blanco, 522; early, 550; John Day, 249, 523, 528, 529; Miocene, 229, 234, 238, 522, 527, 528, 529; Oligocene, 523, 547, 553; Paraná, 227; Pleistocene, 521; Pleisto., S. Amer., 212; Pliocene, 522; Plioc. S. Amer., 226; †primitive, 537; †short-faced, 530; South American, 552; Uinta, 265; White River, 254, 529. (_See also_ Canidæ)

_†Dolichorhinus_, 272, 291

_Dolichotis_, 185

Dolphins, 37, 60, 94, 656; Miocene, 123

Domesticated plants, history of, 288

Douroucoulis, 578, =585=

Drainage, the Pleistocene changes of, 132

Drift-sheets, 25, 132

_†Dromocyon_, 269 (restoration), 271 (restoration), 554, =559=

_†Dromomeryx_, 235, 237 (restoration), 362, =417=

Drought, effects of on mammals, 33

Duck-billed Mole, 57, 59

Dugong, 60, 442

Duplicidentata, 59

Dust, volcanic, 29; wind-blown, 33

East Indian Archipelago, 191

_Echidna_, 57

_Echimys_, 184

Ecuador, 178, 284, 391, 548, 626, 640; Pleistocene, 20, 211; Pliocene, 129

Edentata, 60, 72, 75, 91, 97, 120, 185, 267, 355, =591=; Araucanian, 226; armoured, 60, 592, =610=; Casa Mayor, 283, 592, 595; Deseado, 261, 595; distribution, 138; Eocene, N. Amer., 597, 616; hairy, 60, =591=; Old World, 185, 591; Paraná, 227; Pleisto., N. Amer., 205; Pleisto., S. Amer., 218, 596; Plioc., N. Amer., 225, 597; Plioc., S. Amer., 226, 596; Santa Cruz, 245, 596; South American, 276, 625

Edentates, _see_ Edentata

_†Edvardocopeia_, 509

Egg-laying mammals, 59

Egypt, 254, 370, 422, 432, 442, 450, 587; Eocene, 234; Oligocene, 234, 264, 583

Ei-á, 585

EIGENMANN, C. H., 654

_†Elachoceras_, 443, =449=, (skull fig.), 450, 451, 455

_†Elasmotherium_, 350, 351

Elephant, 590; African, 423 (molar fig.); †Columbian, 195 (restoration), =197=, 198 (restoration), =427=, 430; East African, 425; †Imperial, 199, =427=, 485; Indian, 97 (section of tooth fig.), 197, 423, 425 (manus fig.), 426 (section of fore foot fig.); tribe, 82; West African, 425

Elephantidæ, 432

Elephants, 45, 60, 73, 91, 92, 95, 97, 215, 264, 312, 436, 446, 448, 465, 487, 654; American, 430; cranial bones of, 63; distribution, 138; hairy, 448, proboscis of, 65; Pleistocene, 196, 211, 426; Siberian Pleisto., 39; true, 423, 438, 439; tusks of, 97

_Elephas_, 436, 437 (head and tooth fig.); _E. †columbi_, 195 (restoration), =197=, 198 (restoration), =427=; _E. †imperator_, =199=, =427=, 485; _E. maximus_, 97 (section of molar fig.), 197, 423, 425 (manus fig.); _E. †primigenius_, =196=, 207, 332, =426=

Elk, 50, 141, 151, 155 (fig.); Scandinavian, 151

Elms, 102

†Embrithopoda, 60

Embryology, 648

Emigrants from N. Amer. to Old World, 255, 256, 456

Enamel, 96

England, early Man in, 588; Paleocene flora, 103; Pliocene, 127

_†Enhydrocyon_, 517, =528=, 530

_†Entelodon_, 369

†Entelodontidæ, 250, 361, =366=, 445; Wasatch, 281

†Entelodonts, _see_ †Entelodontidæ, _also_ †Giant Pigs

†Entelonychia, 60, 247, 462, =482=, 652; Casa Mayor, 282; Deseado, 263. (_See also_ †Homalodotheres)

Entrerios, 128

_†Eoanthropus_, 588

_†Eobasileus_, 443, 449, 451, 455

_†Eocardia_, 243

Eocene epoch, 17, =104=; climate of, 26; close of, 111; Europe, 262, 370, 452, 562, 661; North America, =104=, 105 (map), 201, 250, 251, 253, 273, 287, 291, 325, 369, 421, 519, 529, 554, 557, 574, 644; South America, 20, =112=, 261, 281, 477, 481, 482, 485, 487, 488, 508, 509, 512, 514, 625, 642

_†Eodidelphys_, 627

_†Eohippus_, 280, 290, =302=, 303 (restoration), 304, 305 (skull fig.), 307 (manus and pes fig.), 308

_†Eohyus_, 281

_†Eomoropus_, 291, =357=

_†Eotitanops_, 275, 291, =315=

_†Eotylopus_, 257, 362

_†Epigaulus_, 223 (restoration)

_†Epihippus_, 290, =301=, 302

_†Epithelium_, 227, 489, =508=

Epoch, geological, 15

_†Eporeodon_, 361, 375, 379

Equidæ, 290, =291=. (_See also_ Horses)

_Equus_, 95, 199, 213, 223, =291=, 295, 305 (skull fig.), 306 (manus and pes fig.); American species, 296; _E. asinus_, 52; _E. burchelli_, 200; _E. caballus_, 52, 199, 213, 295; _E. †fraternus_, 199; _E. †giganteus_, 200, 201, 295; _E. †occidentalis_, 200; _E. †pacificus_, 201; _E. †pectinatus_, 200; _E. przewalskii_, 52, 292 (fig.); _E. †scotti_, 195 (restoration), =200= (do.); _E. †semiplicatus_, 200; South American species, 307; _E. †tau_, 199, 295

Equus Beds, 33, =131=, 133, 200, 205. (_See_ Sheridan)

Era, geological, 15

_Erethizon_, 151 (fig.), 153, 182, 184, 205

_†Eriodes_, 578

Ermine, 152, 159 (fig.)

Ethiopian region, 146

_†Euceratherium_, 202, 362, 418

_†Eucholœops_, 607

_†Eucinepeltus_, 592, =623=

_†Euprotogonia_, 457, =459=

Eurasia, 110, 548

Europe, 253, 254, 255, 267, 272, 276, 277, 280, 281, 284, 287, 291, 303, 323, 324, 325, 340, 350, 351, 354, 356, 357, 369, 370, 380, 417, 418, 419, 421, 422, 432, 435, 452, 456, 486, 534, 538, 543, 545, 546, 552, 554, 557, 561, 642, 644; caverns of, 30; circumpolar area, 148; Eocene, 104; Eoc. separation from Asia, 104; human habitation of, 588; loess of, 133; mammals of, 145; †Mammoth in, 197; pre-Eocene immigration into, 108; Miocene, 235; Mioc. climate, 122; Pleisto. glaciation, 133; tapirs in, 138; Triassic, 642; zoölogy of, 146

_†Eusmilus_, 254, 517, =538=

_†Eutatus_, 592, 596, =612=, 613

Eutheria, =57=, 59

_†Eutrachytherus_, 263, 462, =477=

Extinction of species, 13, 211

Evolution, of †Amblypoda, 454; of camels, 400; convergent, 649, 650, 655; of †Creodonta, 574; divergent, 18, 139, 650, 655; of Fissipedia, 553; of horses, 305, 325, 400; irreversibility of, 541, 656; modes of Mammalian, 645; of †oreodonts, 381; parallel, 393, 649, 655; of Proboscidea, 436, 437 (diagram); of rhinoceroses, 351; of tapirs, 324; of †titanotheres, =316=, 325

Fallow Deer, 46

Families, distribution of, 138

Fauna, 56; Araucanian, 226; Bridger, 265, =267=, 273, 315; Deseado, =261=, 638; mid. Eocene, 267; John Day, 249; low Miocene, 237; Neotropical, =283=, 610; Oligocene, 237; Paraná, 227; Pleistocene, N. America, =193=, 207; Pleisto., S. Amer., =211=, 226, 597; Puerco, 285; Santa Cruz, 26, 124, =242=, 638; Torrejon, 284; Uinta, =265=, 273; Wasatch, 276; White River, =251=, 265, 266; Wind River, =274=, 275, 315

Faunas, Casa Mayor, 281, 283; Eocene, N. Amer., 265; Eoc., S. Amer., 281; Miocene, 229; Oligocene, N. Amer., 249; Oligo., S. Amer., 261; Paleocene, =283=, 286, 644; Pliocene, N. Amer., 221; Plioc., S. Amer., 225; Quaternary, N. Amer., 193; Quat., S. Amer., 211; successive mammalian, 192; Tertiary, 221; Tertiary, S. Amer., 461

Fawns, 46 (fig.)

Fayûm, 432

Felidæ, 54, 517, 518, =530=

Felinæ, 54, 254, 535, 542, =543=, 650; Miocene, 229, 234, 238, 541, 545; origin of, 659; Pleistocene, 204, 545; Pliocene, 545

_Felis_, 54, 517, =543=, 545, 546; _F. †atrox_, 204, 545; _F. concolor_, 168 (fig.), 544 (skull fig.), 545 (dentition fig.); _F. domestica_, 546 (manus fig.); _F. †imperialis_, 204; _F. leo_, 204; _F. onca_, 176, 177 (fig.), 552; _F. pardalis_, 176 (fig.), 552

Femur, 84, 85 (fig.)

Ferret, Black-footed, 160 (fig.)

_Fiber_, 153

Fibula, 86, 87 (fig.)

Field-mice, 141

FILHOL, H., 534

Fisher, 152

Fishers, 141, 518

Fishes, Florissant, 121; Green River, 109; Panama marine, 23; South American fresh-water, 652; teeth of, 92

Fissipedia, 59, 516, =517=, 553, 554, 555, 556, 557, 558, 563, 576

Flesh-eaters, †primitive, 59, =554=; Santa Cruz, 637

Florida, island, 122; Miocene, 117; Oligocene, 113; Paleocene, 101; Pliocene, 125, 127

Florissant formation, 121

FLOWER, W. H., 389, 390, 411, 412, 419

Flying Lemur, 59

Forests, Oligocene, 538; Paleocene, 102; petrified, 122

Fort Union stage, 17, 99, =102=, 642

Fossils, 7, 29; classification, 55; entombment, 29; evidence of climate, 25; mammals, 61

Fossorial habits, 2

Fox, 191; Arctic, 148, 149 (fig.), 150 (fig.); Grey, 165 (fig.), 517; Red, 158 (fig.), 517

Foxes, 141, 173, 518, 520, 530, 552; grey, 162; Pleistocene, 204; red, 152; White River, 254, 529

France, 256, 333, 364, 441, 574; Eocene, of, 108; Oligocene, 617

Frankstown Cave, 30

Friasian fauna, 509

FÜRBRINGER, M., 655

Gait, varieties of, 90

Galapagos Archipelago, 136

†Ganodonta, 625

_†Garzonia_, 627, =641= (jaw fig.)

†Garzoniidæ, 627

Gazelle, bones of, 35

†Gazelle-Camel, 241, 242 (restoration), =393=, 394, 408

Genera, origin of, 654

Generic area, 137

Genetic series, 56

Genetics, 648

Genus, 53

Geographical changes affecting distribution, 139

Geology, 5

_Geomys_, 163

Geomyidæ, 265

†Giant Pig, 252 (restoration), 260 (do.)

†Giant Pigs, 250, 259, 266, 361, =366=; Bridger, 273, 370; John Day, 259, 367; Miocene, 239, 366, 369; Oligocene, 281, 368; Uinta, 369; Wasatch, 281, 370; White River, 259, =367=

GIDLEY, J. W., 33, 202, 642

Giraffe, 70, 79, 358, 389

†Giraffe-Camel, 236 (restoration), =391=, 392 (restor.)

†Giraffe-camels, 235, =388=, 394; Miocene, 231, 241, 394; Pliocene, 224, 388

Giraffes, 54, 389, 409, 411

Glacial, accumulations, 25; climate, 25, 26; periods, _14_, 25; stages, 17, 130; theory, 129

Glaciation, Pleistocene, 25, 130; causes of, 134

Glaciers, Pleistocene, 131

_†Glossotherium_, 602

_†Glyptodon_, 212 (restoration), 219, 592, =618=, 619 (restor.), 621

†Glyptodont, Santa Cruz, 243 (restoration), 606 (do.)

†Glyptodontia, 60, 245, 246, 592, 593, 594, 595, =617=; Araucanian, 226; Astraponotus, 281, 595, 625; Deseado, 262, 595; Pampean, 212 (restorations), 619 (restorations), 623; Paraná, 227; Pleistocene, N. Amer., 205, 206, 211, 597, 598; Pleisto., S. Amer., 218, 221, 596, 597, 620, 624; Pliocene, N. Amer., 221, 225, 596; Plioc., S. Amer., 596, 622, 624; Santa Cruz, 245, 596, =622=, 623

†Glyptodontidæ, 592

†Glyptodonts, _see_ †Glyptodontia

_†Glyptotherium_, 221, 592

Gnawing mammals, 59

Goat, Rocky Mt., 152, 158 (fig.), 202, 416

Goats, 362, 409, 416

_†Gomphotherium_, 229, =430=, 431 (head restored), 434, 436, 437 (head and molar fig.), 438, 439

Gopher, †Horned, 223 (restoration)

Grasses, 273; Paleocene, 284

Grassy plains, spread of, 233

†Gravigrada, 91, 120, 355, 591, 592, =598=, 612; Pleistocene, N. Amer., 205, 597; Pleisto., S. Amer., 218, 598; Santa Cruz, 605, 607, 609, 610. (_See also_ †Ground-Sloths)

Great Basin, 322; Pleistocene of, 131

Great Britain, 21, 140, 418

Great Plains, 33, 200, 229, 235, 322, 386, 432; Miocene, 121; Oligocene climate, 116; Pleistocene, 131

Greenland, 101, 103, 210; Pliocene, 125

Green River stage, 109

GREGORY, J. W., 35

GREGORY, W. K., 641

_Grison_, 175 (fig.), 517, 552

†Ground-Sloth, giant, 195 (restoration), 603 (restoration); Pleistocene of Cuba, 598; Santa Cruz, 243 (restor.), 606 (restor.); skin of, 40, 602

†Ground-Sloths, 75, 91, 120, 267, 355, 591, 592, 593, 594, 595, =598=; Araucanian, 226; Astraponotus, 595; Casa Mayor, 284, 595; Deseado, 262, 595; Miocene, 609; Mioc., N. Amer., 597; Pampean, 212 (restoration), 220 (do.), 605, 608, 609; Paraná, 227; Pleistocene, N. Amer., 205, 206, 211, 219, 597; Pleisto., S. Amer., 218, 219, 221, 596, 598, 604, 605; Pliocene. N. Amer., 221, 225, 597; Plioc., S. Amer., 596, 598; Santa Cruz, 245, 246, 596, 598, 605, 608, 609. (_See also_ †Gravigrada)

Ground-squirrels, 164, 181

_†Grypotherium_, 592, 602

Guanaco, 60, 139, 178, 389 (fig.), 399 (skull and tooth fig.), 400 (manus fig.), 401 (pes fig.), 490, 491; destruction by cold, 36; distribution, 138

Guiana, 179

Guianas, Miocene, 596

Guinea-Pig, 185; four-toed race, 657, 660

Gulf-coast, Eocene, 104, 111, 117; Miocene, 117; Pliocene, 125

Gulf of Mexico, Eocene, 106, 113; Oligocene, 113, 117; Paleocene, 101

Gulf Stream, Oligocene, 113

_Gulo_, 152, 155 (fig.), 237, 517

Gypsy Moth, 143

HAECKEL, E., 648

Hairless skin, 45

_Halicore_, 442

_†Halmarhiphus_, 627

Handwriting, development of, 9, 13, 14

_Hapale_, 578

Hapalidæ, 172, 578, 582, 583

_†Hapalops_, 243 (restoration), 592, =605=, 606 (restor.), 609 (pes fig.)

Hare, Arctic, 150

Hares, 59, 181, 245, 249; Miocene, 229, 238; Plioc., N. Amer., 222; Plioc., S. Amer., 226; tailless, or whistling, 153

_†Harpagolestes_, 554, =559=, 560, 571

Harrison stage, 120, 235

HATCHER, J. B., 337, 523, 524

Hayti, 173, 185; junction with Centr. Amer., 128; Miocene, 123; Pliocene, 128

Hedgehogs, 59, 276; White River, 253

†Hegetotheriidæ, 462, 472

_†Hegetotherium_, 462, 479

_†Helaletes_, 272, 291

_†Helohyus_, 273, 361, =365=

_†Hemiacodon_, 578

_†Hemipsalodon_, 253, =565=

_†Henricosbornia_, 462

_†Heptodon_, 275, 291, =327=

Herbivora, 516

Herbivorous mammals, 45; large, 44

_†Hipparion_, 291

_†Hippidion_, 212 (restoration), 213, 214 (restor.), 291, 296, =307=, 308 (skeleton fig.)

_Hippocamelus_, 91 (pes fig.), 180, 410 (manus and pes fig.)

Hippopotamus, 45, 54, 60, 70, 92, 358, 654

Hogs, ruminating, 372

Holarctic region, =146=, 147, 150, 588

_†Homacodon_, 273, 361, =398=

†Homalodontotheriidæ, 462; Casa Mayor, 283

_†Homalodontotherium_, 462, =482=

_†Homalodothere_, 482

_†Homalodotheres_, 462, =482=, 509

_†Homo heidelbergensis_, 588; _H. †neanderthalensis_, 588; _H. sapiens_, 588

_†Homunculus_, 578, =586=

Hoofed animals, 74, 77, 81, 83, 89, 312, 313, 461; Araucanian, 227; Bridger, 269, 273; Casa Mayor, 282; clawed, 651; Deseado, 262, 264; massive, 654; Miocene, 229, 234; Paraná, 228; Pleistocene, N. Amer., 199; Pleisto., S. Amer., 213; †primitive, 492; Santa Cruz, 246; Torrejon, 285; Uinta, 273; Wasatch, 277; Wind River, 274 (_see_ Ungulata)

Hoofed mammal, clawed, 484

Hoofed mammals, 60, 456, 459, 460; even-toed, 54, 60; odd-toed, 60; White River, 255 (_see_ Ungulata)

HOOKER, J., 193

_†Hoplophoneus_, 252 (restoration), 517, =535=, 536 (restoration), 539, 540, 543

Horn-cores, 416

Horse, 44, 48, 52, 62, 76 (scapula fig.), 79 (humerus fig.), 81 (fore-arm bones fig.), 85 (femur fig.), 87 (leg-bones fig.), 95 (molar fig.), 294, (manus and pes fig.), 359; Asiatic Wild, 52, 292 (fig.); †Dawn, 302, 303 (restoration); †forest, 200; †Pampas, 212 (restoration), 214 (restoration), 308 (skeleton fig.); †Texas, 195 (restoration), 200 (restoration); †three-toed grazing, 298 (restoration); True, 199, 213, 295; †White River, 252 (restoration), 300 (restoration). (_See also_ _Equus_)

Horses, 56, 60, 81, 95, 97, 289, 290, =291=, 312, 319, 330, 353, 360, 382, 397, 458, 461, 499, 504, 651, 653, 655, 656, 658, 661; Blanco, 222; bones of, 33; Bridger, 272, 302; browsing, 223, 231, 235, 297, 298; Eocene, 304, 307; grazing, 223, 231, 235, 297, 298; John Day, 299; Miocene, 295, 297, 298, 231, 232, 234, 238, 301; North American, 39; Oligocene, 299; phyla of, 289, 650; Pleistocene, N. Amer., 199, 208, 211, 213, 221, 295, 304, 307; Pleisto., S. Amer., 213, 215, 307; Pliocene, 223, 295, 307, 331; South American, 307; spread of, 142, 143; three-toed, 33, 501; tridactyl, 658; true, 292, 308; Uinta, 301; Wasatch, 280, 302; White River, 257, 299, 300; Wind River, 275, 302, 303, 396. (_See also_ Equidæ)

HORSFALL, R. B., 42

HRDLIČKA, A., 589

Hudsonian fauna, 151

Hudson’s Bay slope, interglacial forests, 131

Huemul, 180

Humerus, 78 (fig.)

Humid province, 164

Humidity, effect on distribution, 141

Hungary, 316

Hutias, 184

HUXLEY, T. H., 28

Hyænidæ, 518

_†Hyænodon_, 252 (restoration), 253, 555, =562=, 563 (restoration), 564 (skeleton fig.), 565 (teeth fig.), 566 (teeth fig.), 567, 576

†Hyænodont, primitive, 567 (restoration)

†Hyænodontidæ, 253, 555, 557, =562=, 565 (teeth fig.), 566 (teeth fig.), 569, 573, 575; Bridger, 268; Eocene, 254, 566, 576; Wind River, 274

†Hyænodonts, _see_ †Hyænodontidæ

_†Hyænognathus_, 522, 524, 530

_Hydrochærus_, 183 (fig.), 185, 205

_Hydropotes_, 412

Hyena, bones of, 35

†Hyena-dogs, 222, 249, 527, 530

Hyenas, 518, 527, 553, 554

Hyoid arch, 67

†Hyopsodonta, 59

_†Hyperhippidium_, 213, 291, =307=

_†Hyperleptus_, 607

†Hypertragulidæ, 267, 362, 386, =402=, 414; Eocene, 408; John Day, 251, 404, 407; Miocene, 241, 258, 404; White River, 258, 406, 408

†Hypertragulids, _see_ †Hypertragulidæ

_†Hypertragulus_, 241, 258, 267, 362, =407=, 408

_†Hypisodus_, 258, 362, =408=

_†Hypohippus_, 291, 297, 300

Hypsodont teeth, 95 (fig.); prevalence of, 232

_†Hyrachyus_, 271 (restoration), 272, 291, 339, =344= (restor.), 345 (skull fig.), 346, 349, 350

_†Hyracodon_, 252 (restoration), 255, 266, 291, =341= (restor.), 343 (manus fig.)

†Hyracodontidæ, 291, =403=

†Hyracodontinæ, 291, 340, =341=, 346, 350, 351, 352; Bridger, 272, 343; Eocene, 342; Uinta, 266, 343; White River, 255, 256, 341; Wind River, 275, 276, 344

†Hyracodonts, _see_ Hyracodontinæ

Hyracoidea, 60, 458, 481, 492, 514; distribution, 138

Hystricomorpha, 245, 262

Ice Age, 25

_Ichthyomys_, 182

_Icticyon_, 174, 212, 517, 527, 552

_†Ideodidelphys_, 627

IHERING, H. VON, 124

_†Ilingoceros_, 362

Ilium, 77

Immigrants from Old World to N. America, 229, 276, 279, 316, 365, 370, 386, 416, 417; artiodactyls, 201, 202, 259; bison, 420; Carnivora, 203; felines, 258; †hyænodonts, 254; insectivores, 253; mustelines, 238, 254; otters, 234; Proboscidea, 422; rhinoceroses, 234; sheep, 419; from North to South America, 171, 211, 226, 227, 242, 461; from South to North America, 205, 206, 233

Immigration, 266; Eocene, 324; Miocene, 233; Pleistocene, 151; Pliocene, 151

Incisors, 93

India, 14, 213, 327, 390, 412, 418, 430, 527, 542, 551; Permian glaciation of, 25

Indian Ocean, 442

Indians, pre-Columbian, 590

_†Indrodon_, 580

Insect-eaters, 92

Insectivora, 59, 191, 249, 459, 580; Bridger, 268; Miocene, 238; Neotropical, 172; Paleocene, 284; Puerco, 286; Santa Cruz, 245, 587; Torrejon, 285; Uinta, 265; Wasatch, 276; White River, 253; Wind River, 274

Insectivores, _see_ Insectivora

Inserts, 141; Florissant, 121; Green River, 109

Interglacial stages, 17, 130, 207; climate of, 134; mammals of, 131

†Interatheriidæ, 462, 476, =479=

_†Interatherium_, 462, =481=, 636 (restoration)

Irreversibility of evolution, 541, 656

_†Ischyrocyon_, 517

†Ischyromyids, Bridger, 270; Uinta, 265; Wasatch, 280

_†Ischyromys_, 254

_†Isectolophus_, 291

†Isotemnidæ, 462, =485=

_†Isotemnus_, 462

Isthmian region, geology, 120; Pliocene, 128

Isthmus of Panama, 170; geology, 21, 22; Miocene, 123; Oligocene, 117, 123; Pleistocene, 122, 134

Jackal, bones of, 35

Jaguar, 176, 177 (fig.), 212, 545, 552

Jamaica, Miocene, 123; mongoose introduced, 142

Japan, 135

Java, 21, 140, 327

JEFFERSON, T., 206, 597

Jerboas, 90

John Day age and stage, 17, 30, =116=, 375, 543

Jumping Mouse, 153, 160 (fig.); mice, 182; shrews, 59

Jurassic period, 15, 16, 642, 643

Kangaroo-rats, 163 (fig.), 182; Miocene, 238

Kangaroos, 59, 626, 640

Kinkajou, 175 (fig.), 517, 546, 552

Klipdasses, 458, 481

KNIGHT, C. R., 42, 470, 478, 480, 481, 494, 502, 506, 606, 636, 639

KOWALEVSKY, W., 233, 503

Kudu, 225

Labrador, Pliocene, 125

_Lagidium_, 185

Lake, Argentine, 36; Bonneville, 131; Callabonna, 34; Lahontan, 131; Ontario, invasion by sea, 132

Lakes, relation to glaciation, 132; sediments of, 37

_Lama_, 138, 362, =388=; _L. huanacus_, 178, 389 (fig.); _L. vicunia_, 178 (fig.)

_†Lambdaconus_, 489

_†Lambdotherium_, 275, 291, =315=

Land-bridges, 18

Land-connections, how ascertained, 20; Cuba and Centr. Amer., 128; Hayti and Centr. Amer., 128; N. Amer. and Asia, 18, 125, 588; N. Amer. and Europe, 18, 106, 108, 109, 118, 120; N. Amer. and Old World, 21, 23, 109, 115, 249, 251, 267, 276, 287; N. and S. Amer., 100, 120, 123, 233; S. Amer. and Africa, 103, 112, 124, 587; S. Amer. and Antarctica, 112, 124; S. Amer. and Australia, 103, 123, 638; S. Amer. and Old World, 262; West Indies and Mediterranean lands, 120

La Plata, estuary, 34

Last Hope Inlet, 60

_Latax_, 517

Lava-fields, the Columbia River, 121, 127

Lavas, Miocene, 118, 121, 122; Pleistocene, 133; Pliocene, 127

LECHE, W., 63

LEIDY, J., 372

Lemming, 148

Lemmings, 141, 153

Lemur, †monkey-like, 581 (head restored)

_Lemur_, 578

Lemuroidea, 60, 284, 459, 577, =578=, 588; Bridger, 270, 578; Eocene, 579; Wasatch, 281, 580; Wind River, 275

†Leontiniidæ, 462, =475=

_†Leontinia_, 263 (head restored), 462, =475=

Leopard, 45; Hunting, 543

_†Leptarctus_, 517, 547

_†Leptauchenia_, 258, 361, =377= (skull fig.), 378 (restoration), 381

†Leptochœridæ, 361

_†Leptochœrus_, 361

_†Leptomeryx_, 258, 267, 362, =407= (skull fig.), 409, 563 (restoration), 657

_†Leptoreodon_, 362

_†Leptotragulus_, 267, 362

_Lepus_, 164

_†Lestodon_, 602

_†Limnocyon_, 555, =573=

Linnæan system, 51, 56, 57

LINNÆUS, C., 1, 51, 52, 55, 578

Lion, 45, 48, 92, 204; cubs, 46

Lions, 210, 212

Lipotyphla, 59

_†Listriodon_, 364

†Litopterna, 60, 469, =489=, 514, 651, 653; Araucanian, 227; Casa Mayor, 283; Deseado, 264; Pampean, 212 (restoration), 216 (do.); Paraná, 228; Pleistocene, 215, 221; Santa Cruz, 243 (restorations), 247

Lizards, 102; Santa Cruz, 244

Llama, 54, 60, 490, 491; distribution, 138

Llama-like animals, 386

Llamas, 13, 90, 241, 257, 362, 386, =388=, 390, 391, 421, 461; Pleistocene, N. Amer., 196, 202; Pleisto., S. Amer., 213, 215; Pliocene, 224; South American, 231

Loess, 133

_Loncheres_, 184

LOOMIS, F. B., 487

†Lophiodontidæ, 257, 272, 291, 319, 325, =326=, 341, 343, 348; Eocene, 326; Oligocene, 339; Wasatch 280, 326; White River, 257, 326; Wind River, 275, 315

†Lophiodonts, _see_ †Lophiodontidæ

Loricata, 592, =610=

Loup Fork age and stage, 17, =121=

Loup River stage, 127

Lower Sonoran zone, 148, 164

Lowest Eocene, 99

_Loxodonta_, 423 (molar fig.)

LUCAS, F. A., 337

LULL, R., 437

Lunar, 83

_Lutra_, 152, 160 (fig.), 164, 175, 213, 517, 551

_Lutreola_, 152 (fig.)

LYDEKKER, R., 150, 181, 389, 390, 411, 412, 419

_Lyncodon_, 175, 552

_Lynx_, 153, 163, 169 (fig.), 517, 544 (dentition fig.)

Lynxes, 141, 176, 543, 544, 552; Pleistocene, 204

†Machairodontinæ, 54, =530=, 535, 542; cursorial, 543; Oligocene, 535

†Machairodonts, _see_ Machairodontinæ, _also see_ †Sabre-tooth tigers

_†Machairodus_, 517, =534= (skull fig.), 536

_†Machairoides_, 555, =573=

_†Macrauchenia_, 212 (restoration), 215, 216 (do.), 217, 227, 248, =489=, 493, 495, 496 (skull fig.), 497 (do.), 498

†Macrauchenid, Santa Cruz, 494 (restoration)

†Macrauchenidæ, 248, =489=, 496 (skull fig.), 497 (do.), 651; Deseado, 264, 499; Eocene, 499; Paraná, 228, 496; Pleistocene, 489; Pliocene, 493; Santa Cruz, 248, 493

_†Macrotherium_, 354

Madagascar, 173, 530; Pleistocene, 579; zoölogy of, 146

Magnum, 83

Malagasy region, 146

Malay Archipelago, 146, 191, 580; islands, 281, 327, 408; Peninsula, 137, 281

Malleolar bone, 87

Mammal, defined, 1

Mammalia, classification, 50; evolution of, 645; geographical distribution, 135; skeleton and teeth of, 61

†Mammoth, 39, =196=, 207, 332, =426=, 427, 429; Siberian, 44

Man, 60, 62, 66, 76 (scapula fig.), 77 (clavicle fig.), 79 (humerus fig.), 80 (fore-arm bones fig.), 82 (manus fig.), 84, 88 (pes fig.), 90, 93, 577, 578, 582; American Pleistocene, 589; European Palæolithic, 197; European Pleistocene, 39, 588; origin of, 588; in Western Hemisphere, 588

Manatee, 207, 442

_Manatus_, 442

_†Manteoceras_, 272, 317 (head restored)

Manus, 82 (fig.)

Maples, 102

Mara, 185

Marine, fauna, Miocene, 117; Oligocene, 117; Pliocene, 127; habit, 2; mammals, 37, 45; rocks, 37; shells, Pleistocene, 132; Pliocene of England, 127

_Marmosa_, 632

Marmoset, 584 (fig.)

Marmosets, 172, 578, =582=, 583

Marmot, 150, 152 (fig.)

_Marmota_, 152 (fig.), 153

Marmots, 60, 141, 153, 181, 245; Miocene, 229; Pliocene, 222

MARSH, O. C., 318

Marsupial, †allotherian, 286 (head restored), predaceous, Santa Cruz, 243 (restoration), 494 (do.), 636 (do.), 639 (do.)

Marsupialia, 43, 57, 59, 459, =626=; Araucanian, 226, 634; Australian, 145, 632, 638; Bridger, 268; carnivorous, 59; Casa Mayor, 282, 638, 642; Deseado, 261, 638, 642; distribution, 138; flesh-eating, 553; herbivorous, 59; insectivorous, 59; Miocene, S. Amer., 226; Paleocene, 284; Paraná, 227, 634, 641; predaceous, 627, =632=; Puerco, 286, 642; Santa Cruz, 244, 635, 640; South American, 190, 638; Torrejon, 285, 642; Wasatch, 276; White River, 251

Marten, 551

Martens, 152, 231, 517, 550, 551; Miocene, 229; Pleistocene, 204

_Martes_, 517

†Mastodon, 207, 426, 590; American, 195 (restoration), 196, 207, 229 (molar fig.), 428, (restoration), =429=, 437 (head fig.), 438, 439, 448; Miocene, 431 (head restored)

_†Mastodon_, =429=, 430, 437 (head and molar fig.); _†M. americanus_, _see_ †Mastodon, American; _†M. andium_, 436

†Mastodons, 60, 264, 430, 438; Blanco, 222; early, 432; Miocene, 229, 234; Pleistocene, N. Amer., 196, 211; Pleisto., S. Amer., 215, 221, 436; Pliocene, 225; Tertiary, 429

MATTHEW, W. D., 241, 257, 407, 409, 414, 531, 532, 540, 542, 546, 547, 565, 566, 657, 659

_Mazama_, 180, 181 (fig.), 362

Meadow-mice, 153, 182, 218

Mediterranean, Eocene, 104, 106

_†Megalictis_, 517, =551=

_†Megalocnus_, 592, =604=

†Megalonychidæ, 592, =598=, 610

_†Megalonychotherium_, 592

_†Megalonyx_, 195 (restoration), 206, 219, 221, 592, 597, =604=, 607

_†Megamys_, 226

_†Megatheriidæ_, 591, =598=, 607

_†Megatherium_, 206, 212 (restoration), 220 (do.), 591, 597, =599=, 602, 604, 608

_Mellivora_, 551

†Meniscotheriidæ, 457, =458=

_†Meniscotherium_, 457, =458=, 459 (restoration)

Menotyphla, 59

_Mephitis_, 153, 167 (fig.), 517, 552

MERRIAM, C. H., 140, 141, 147, 148, 150, 161

MERRIAM, J. C., 31, 32, 538, 543

_†Merychippus_, 291, =297=, 298

_†Merychyus_, 232, 361, 372, =373=, 374, 377, 381, 382

_†Merycochœrus_, 241, 361, 372, =373= (head restored), 374, 376, 381, 382 (manus fig.)

†Merycodontidæ, 362, =414=

_†Merycodus_, 224, 362, =414=, 415 (restoration), 417

_†Merycoidodon_, 252 (restoration), 258, 259 (do.), 361, =379= (skull fig.), 382 (manus fig.), 536 (restoration)

_†Mesatirhinus_, 271 (restoration), 314 (do.)

Mesaxonic symmetry, 359

_†Mesocyon_, 517, =528=, 530

_†Mesohippus_, 252 (restoration), 290, =300= (restor.), 302, 305 (skull fig.), 308 (manus and pes fig.), 326, 342, 343, 396, 397, 505

†Mesonychid, 269 (restoration), 271 (do.)

†Mesonychidæ, 554, 556, =558=, 574; Bridger, 268, 559; Torrejon, 285, 560; Uinta, 265, 559; Wasatch, 277, 560; Wind River, 274

_†Mesonyx_, 554, =559= (teeth fig.), 561

_†Mesoreodon_, 361, 372, =378=

Mesozoic era, 15, 16, 18, 23, 103, 284, 574, 632, 643

Metacarpal, 84

Metacarpus, 83

_†Metacheiromys_, 592, =616=

_†Metamynodon_, 255, 291, =346=, 347 (restoration), 352, 510

Metapodial, 90

Metatarsal, 89

Metatarsus, 89

Metatheria, 626

_†Meteutatus_, 592

Mexico, 33, 179, 181, 199, 200, 207, 229, 419, 427, 585; Eocene, 104; lowlands, 142, 146, 164; mammals, 135, 141, 142; Miocene, 118, 121; plateau, 142; Pliocene, 125

_†Miacidæ_, 527, 530, 554, 555, 556, =557=, 562, 576; Bridger, 268; Torrejon, 285; Uinta, 519, 558; Wasatch, 277, 279; Wind River, 274

_†Miacis_, 555, 558

Mice, 60, 244; groove-toothed, 182; John Day, 249; jumping, 182; Miocene, 229; Pleistocene, S. Amer., 218; vesper, 182; white-footed, 153, 164, 182; White River, 254

_†Microbiotherium_, 627

_Microtus_, 153, 218

_Midas_, 578

Migration, of birds, 143; of mammals, 18, 19, 143; of †hyænodonts, 567; between N. and S. Amer., 129; Oligocene, 254; Pleistocene, 207, 211; pre-Wasatch, 108; of Proboscidea, 441; White River, 116

Milk-dentition, 94

Mink, 152 (fig.)

Minks, 213, 518, 550; Pleistocene, 204

Miocene epoch, 17, 33, 112; North America, =117=, 119 (map), 233, 249, 251, 284, 386, 420, 421, 438, 554, 658, 661; European, 235, 364, 435, 441, 550; South American, 20, =123=, 242, 261, 553, 640

_†Miohippus_, 290, 299

_†Miolabis_, 362, =391=

Mississippi, Embayment, 104, 117; Valley, loess of, 133

Missouri River, drowning of bison in, 36

MITCHELL, P. CHALMERS, 52

_†Mœritherium_, =434=, 437 (head and molar fig.), 438, 439, 440, 441, 442, 450

Molars, 93

Mole, 2; Star-nosed, 152

Moles, 59, 77, 89; American, 163; Bridger, 268; golden, 245; White River, 253

Mole-shrews, 153

Mongoose, 142

Monkeys, 2, 60, 141, 282, 283, 284, 577, 578, =582=; Bridger, 270; eastern hemisphere, 172; howling, 578, =585=; Neotropical, 172, =586=; New World, 583, 587; Old World, 583, 587; Pleistocene, 218, 586; Santa Cruz, 245, 586, 587; South American, 578, =583=, 587; spider, 578, =584=; Wind River, 275

Monodelphia, =58=, 59, 145

Monotremata, 59; distribution, 138

Monte Hermoso age and stage, 20, =129=, 226, 479, 499, 508, 634

Moose, 4, 65, 141, 151, 156 (fig.), 181, 202, 208, 411, 412, 413

Moraine, Great Terminal, 131

Moraines, 25

_†Moropus_, 238, 240 (restoration), 291, =356= (manus fig.)

_†Morphippus_, 462

_Moschus_, 412

Mt. Hood, 121; Kenya, 134; Tacoma, 121

Mountain Lion, 153, 168 (fig.)

Mountain ranges, as barriers to mammals, 142; history of, 23

Mouse, Jumping, 153, 160 (fig.)

Mouse-Deer, 54, 60, 358, 408. (_See also_ Chevrotains _and_ Tragulina)

†Multituberculata, 642

Mummies of Pleistocene rodents, 40

Muntjac, Indian, 412

Muntjacs, 412, 414, 658

Musk-Ox, 148, 149 (fig.), 202, 207, 211, 418

Musk-Oxen, 27, 141, 208, 210

Muskrat, 2, 151, 153, 182

_Mustela_, 159 (fig.), 160 (fig.), 517

Mustelidæ, 174, 222, 265, 517, 518, =550=, 553, 554; John Day, 249; Miocene, 238, 551; Old World origin, 550; Pleistocene, 551; Pleisto., S. Amer., 213; Pliocene, 223, 551; South American, 552; White River, 254, 551

Mustelines, _see_ Mustelidæ

Mutation, 662

_Mycetes_, 585

†Mylagaulidæ, 222, 229, 233

†Mylagaulids, _see_ †Mylagaulidæ

_†Mylodon_, 206, 212 (restoration), 219, 592, 597, 601, =602=, 603 (restoration), 604, 607, 608 (pes fig.)

†Mylodontidæ, 206, 592, 598, 602; Deseado, 610; Santa Cruz, 605, 607, 609

†Mylodonts, _see_ †Mylodontidæ

_Myocastor_, 184

_Myodes_, 153

_Myrmecophaga_, 91, 187, 188 (fig.), 206, 355, 591, 600

Myrmecophagidæ, 591

Mystacoceti, 60

_Nasua_, 162, 176, 213, 517, 546, 552

Nasuas, 141

Navicular, 88

Navidad formation, 124

†Necrolestidæ, 245

_†Nematherium_, 592, 607

Neogæa, 145

Neogæic realm, 146, 164

_†Neohipparion_, 33, 291, 298 (restoration), 299 (skeleton fig.)

_†Neoplagiaulax_, 627

_Neotoma_, 153, 164

_†Neotragocerus_, 362

Neotropical region, 146, 147, =164=, 170 (map), 322, 363, 418, 436, 461, 552, 583, 591, 630

_†Nesodon_, 243 (restoration), 462, =467= (skull fig.), 470 (restoration), 473 (pes fig.), 474, 475, 478, 482, 483, 498, 510, 511

NEUMAYR, M., 663

New Guinea, 634

New York Zoölogical Society, 148, 149, 150, 151, 152, 154-169, 176-180, 182, 183, 186, 188, 189, 190, 292, 389, 584

Newfoundland, Pliocene, 125

New Zealand, 284; Miocene, 123

Nicaragua, 218

_†Nimravus_, 249, 541, =542= (skull fig.), 543

Nomenclature, 50

North America, the circumpolar area, 148; mammals of, 145; zoölogical divisions, 146, 147 (map)

†Notharctidæ, 578

_†Notharctus_, 578, =579=

_†Nothocyon_, 530

_†Nothrotherium_, 592

†Notohippidæ, 262, 462, =475=

_Notohippus_, 462, =476=

Notopithecidæ, 462

_†Notopithecus_, 462

†Notostylopidæ, 282, 462, =485=

_†Notostylops_, 462

Notostylops Beds, 20, 281

Notoungulata, 461, =489=

Nova Scotia, Pliocene, 125

_Nyctipithecus_, 578, =585=

Oaks, 102

Ocelot, 176 (fig.), 212, 552

_Ochotona_, 153

_Octodon_, 184

Octodontidæ, 184

_†Octodontherium_, 262

_Odocoileus_, 95 (molar fig.), 153, 162, 202, 208, 360 (molar fig.), 362, 413; _O. hemionus_, 46 (fawns fig.), 167 (fig.); _O. virginianus_, 166 (fig.), 179, 412; _O. virg. osceola_, 179 (fig.)

Odontoceti, 60

Okapi, 45

Old World, 101, 258, 266, 295, 327, 331, 332, 335, 341, 351, 353, 358, 386, 390, 413, 420, 426, 518, 550, 554, 558, 562, 583; camels, 138; horses, 201; mammals, 120, 121, 142; separation from N. A., 146

_†Oligobunis_, 517, =551=

Oligocene epoch, 17; Europe, 324, 352, 370, 543, 552, 661; North America, =113=, 114 (map), 204, 224, 265, 287, 378, 576, 658; South America, 20, =117=, 282, 456, 485, 508, 512, 625

_†Omomys_, 578

_†Onohippidium_, 307

Ontogeny, 648

_†Oödectes_, 555, 558

Opossum, 161 (fig.), 627; Water-, 627, 631

Opossum-like forms, Cretaceous, 638

Opossums, 2, 58, 59, 141, 161, 249, 626, 627, =630=; Araucanian, 226; Bridger, 268; Casa Mayor, 282; Cretaceous, 631; Eocene, 631; European, 631; North American, 631; Oligocene, 631; Paleocene, 631; Paraná, 227; Pleistocene, 221; Santa Cruz, 244; South American, 190, 221, 631; White River, 251; Wind River, 274; woolly, 631

_Opsiceros_, 327, 329, 330, 332, 350, 351

Orders, distribution of, 138

Ordovician period, 15

_Oreamnos_, 152, 158 (fig.), 202, 416

_†Oreodon_, 379

†Oreodont, White River, 252 (restoration), 259 (do.), 536 (do.)

†Oreodontidæ, 250, 361, =372=, 383, 384, 385, 404, 436, 652, 661; Eocene, 372, 381; grazing, 232; John Day, 250, 375, 377, 379; Miocene, 231, 235, 241, 372, 374; Pliocene, 225, 373; Uinta, 267, 380; White River, 258, 377

Oriental region, 146

_Ornithorhynchus_, 57

_†Orohippus_, 272, 290, =302=

OSBORN, H. F., 18, 59, 102, 193, 194, 199, 207, 235, 241, 265, 273, 288, 297, 331, 340, 341, 345, 357, 406, 409, 414, 427, 450, 554, 655

_Otocyon_, 656

Ottawa valley, marine invasion of, 132

Otter, 2, 160 (fig.), 175, 213

Otters, 152, 164, 516, 517, 518, 550, 551; Miocene, 229, 234; Pleistocene, 204; South American, 552

_Ovibos_, 149 (fig.), 202, 208, 362, 418

_Ovis_, 152, =419=

Ox, 70

Oxen, 54, 60, 362, 409, 416, 418

_†Oxyæna_, 274, 277, 555, 565 (teeth fig.), 566 (do.), =571=, 572 (restoration), 573

_†Oxyænidæ_, 555, =568=, 575; Bridger, 268, 568, 573; Uinta, 265, 573; Wasatch, 277, 571; Wind River, 274, 571

_†Oxyænodon_, 555

†Oxyclænidæ, 554, 561, =562=, 568, 574

_†Oxyclænus_, 554

_†Oxydactylus_, 241, 362, =391=, 392 (restoration), 393 (skeleton fig.)

OWEN, R., 217, 463, 467, 510, 603, 608

Paca, 183 (fig.), 185

_†Pachyæna_, 274, 277, 554, =560=

_†Pachycyon_, 522

Pachydermata, 44, 490, 492, 654

_†Pachyrukhos_, 227, 462, =478=, 479, 639 (restoration)

Pacific Coast, Eocene, 104, 111; mingling of mammals, 140; Miocene, 117, 120; Oligocene, 113; Paleocene, 101; Pleistocene, 132; Pleisto. volcanoes, 133

_†Palæarctonyx_, 555

_†Palæomastodon_, =432=, 434, 435, 436, 437 (head and molar fig.), 438, 439, 440, 441, 450

_†Palæonictis_, 277, 555, =574=

Palæontological method, 9, 11, 29

Palæontology, 29, 649, 660, 663

_†Palæosyops_, 272, 291, 314 (molar fig.), 317 (head restored), 318 (manus fig.)

_†Palæothentes_, 627

_†Palæotherium_, 490, 492, 661

Palæozoic era, 15

_†Palæpanorthus_, 627

Paleocene epoch, 17, =99=, 108, 253, 273, 276, 291, 443, 453, 454, 456, 459, 460, 519, 554, 557, 558, 560, 561, 562, 568, 578, 580, 625, 642

Palms, 103, 111, 116, 122

_†Paloplotherium_, 661

Pamir, 419

Pampas, 133, 142, 211, 213, 218, 219, 596

Pampean Beds, 19, 133, 136, 228, 248, 463, 471, 478, 489, 493, 496, 498, 586; mammals, =212= (restorations), 489

Panda, 546

Pangolins, 60, 353

_†Panochthus_, 592, =618=, 620

†Pantodonta, 443, =451=

_†Pantolambda_, 285 (restoration), =453=, 454

Paraguay, 164, 178, 189

_†Parahippus_, 290, =297=

_†Parahyus_, 281, 361, =370=

Parallelism, 397, =649=, 652, 653

_†Paramylodon_, 592

_†Paramys_, 270, 271 (restoration), 280

Paraná age and stage, 20, =128=, 242, 493, 499, 507, 635

Paraná River, 34

_†Parapithecus_, =583=, 587

_†Parastrapotherium_, 509, =512=

Paraxonic symmetry, 359

Patagonia, 30, 40, 139, 178, 180, 184, 185, 189, 190, 191, 242, 263, 463, 467, 477, 586, 596; Cretaceous, 117, 632; Eocene, 112, 117; marine rocks, 112; Miocene, 123, 613; Oligocene, 117; Pleistocene glaciation, 133; Pliocene, 128; Tertiary, 20

Patagonian age and stage, 20, =123=, 474, 475, 479

Patella, 86 (fig.)

_†Patriofelis_, 271 (restoration), 274, 555, =568=, 569 (restoration), 570 (pes fig.)

_†Paulogervaisia_, 462, =488=

Peace Creek stage, 127, 221, 322

Peccaries, 141, 178, 361, =363=, 461; Bridger, 273, 365; John Day, 250, 365; Miocene, 232, 235, 239, 365; Oligocene, 365; Pleistocene, 201; Pleisto., S. Amer., 213, 215; Pliocene, 224, 226, 364; Uinta, 266, 365

Peccary, 33, 60, 161, 177 (fig.), 222, 360 (molar fig.)

Pecora, 54, 60, 362, 387, 402, =409=, 420, 421; Neotropical, 179; Oligocene, 421; Pleistocene, 201

_†Pelecyodon_, 592

†Peltephilidæ, 592

_†Peltephilus_, 592, =613= (skull fig.), 615

Pelvis, 77

_†Pelycodus_, 578, =580=

PENCK, A., 134

_†Peraceras_, 332

_Perameles_, 58

_Peramys_, 631

_†Peratherium_, 627, 631

_†Perchœrus_, 361, =365=

†Periptychidæ, 443

_†Periptychus_, 443, =454=

Perissodactyla, 60, 247, 248, 284, =288=, 310, 353, 354, 358, 359, 360, 383, 402, 450, 458, 484, 485, 491, 499, 507, 514, 651, 653; Bridger, 270, 344; †Clawed, 60, =353=; Eocene, 289, 338, 339, 352, 354, 359; John Day, 250; Miocene, 230, 234, 238; Neotropical, 176; normal, =291=, 355; Pleistocene, N. Amer., 199; Pleisto., S. Amer., 213; Uinta, 266; Wasatch, 280; of western hemisphere, 322; White River, 255; Wind River, 275

Perissodactyls, _see_ Perissodactyla

Permian period, 15; climate of, 24, 25; glaciation, 25

Peru, 178, 179, 180, 184, 356, 393, 548

Petrifaction, 40

Petrified forests, 122

_Phacochœrus_, 363

Phalangers, Australian, 244, 626, 640, 641, 642

Phalanges, 84

_†Pharsophorus_, 627

†Phenacodontidæ, 457

_†Phenacodus_, 277, 278 (restoration), 285, =457= (skeleton fig.), 458, 459

Philippines, 579

Philology, 646

_†Phlaocyon_, 238, 517, =547=

Pholidota, 60, 353

Phylogeny, 648

Phylum, 56

Pichiciago, 190, 592, 611

Pig, 359 (fore-arm bones and manus fig.), 360 (pes fig.); Wild Texas, 161

Pigs, 281

Pikas, 59, 153, 181

Pilosa, 60, 591, =592=

Pinnipedia, 59, 516

Pisiform, 83

_Pithecia_, 578, =585=

_Pitheculus_, 578

Placenta, 58

Placental mammals, 58, 59, 145

_†Plagiarthrus_, 481

†Plagiaulacidæ, 627

_Plagiodontia_, 185

_†Planops_, 591

Plant-feeders, 92, 95

Plantigrade, 90

Plants, distribution, 141; Florissant, 121, 122; Green River, 109; Miocene, 122; Miocene of Andes, 124; Mioc. of Europe, 122; Oligocene of Alaska, 116; Oligo. of Europe, 116; Pliocene, 127

Plateau region, 101, 111, 122; Pleistocene upheaval of, 133

Plateaus as affecting spread of mammals, 142

_†Platygonus_, 33, 202, 222, 361, =364=

Platyrrhina, 578, =583=, 587

Pleistocene epoch, 17, =129=, 130, 172, 229, 239, 245, 246, 263, 264, 299, 324, 332, 335, 336, 350, 351, 354, 364, 365, 386, 391, 412, 413, 415, 416-419, 426-429, 436, 438, 439, 448, 485, 499, 518, 524, 530, 531, 545, 549, 551, 552, 586, 588, 614, 631, 632; climate, 25; effects of climate on animal distribution, 192; glaciation, 25; European, 661; lowest, 127; mammals, 195 (restorations); South American, 19, 20, 133, 296, 465, 476, 479

_†Pleurocœlodon_, 462

_†Pliauchenia_, 362

PLINY, letter on eruption of Vesuvius, 30

Pliocene epoch, 17, 112, =125=; North American, 126 (map), 199, 201, 202, 229, 233, 238, 242, 245, 246, 248, 258, 263, 282, 295, 298, 299, 324, 327, 333-336, 340, 353, 354, 356, 357, 364, 365, 370, 372, 373, 386, 388, 390, 391, 413, 414, 416, 417, 421, 427, 429, 430, 435, 436, 485, 486, 493, 499, 507, 508, 524, 527, 530, 531, 534, 536, 545, 546, 547, 549-552, 554, 598, 612, 614, 632; South American, 20, =128=, 466, 467, 479

_†Pliohippus_, 291, =296=, 307

Pocket-gophers, 163, 164, 182; John Day, 249; Miocene, 229, 238; Pliocene, 222; Uinta, 265

Pocket-mice, 191

_†Poëbrotherium_, 252 (restoration), 257, 362, =394= (restor.), 397, 399 (skull and tooth fig.), 400 (manus fig.), 401 (pes fig.)

_†Pogonodon_, 535, =541=

†Polydolopidæ, 627, =642=

_†Polydolops_, 627

_†Polymastodon_, 286 (head restored), 627

Polyprotodonta, 59, 627, =630=, 640, 641

Pompeii, 30

Poplars, 102

Porcupine, Brazilian Tree, 182 (fig.); Canada, 5, 151 (fig.), 153, 182, 205; Short-tailed, 150, 182, 205

Porcupine group, 182, 262; suborder, 245

Porcupines, 59, 184; short-tailed, 141; tree, Pleistocene, 218; tree, Santa Cruz, 245

Porpoises, 3, 37, 45, 60, 94, 442, 656

Port Kennedy Cave, 30, 210

Port St. Julian, 489

Portugal, caverns, 40

_Potos_, 175 (fig.), 517, 546, 552, 558

Pouched mammals, 57, 59. (_See also_ Marsupialia)

_†Prœuphractus_, 592

Prairie-Dog, 169 (fig.)

Prairie-dogs, 164, 181

_Praopus_, 611

Pre-Cambrian eras, 15

Premolars, 93

Pre-occupation, 142

_†Prepotherium_, 591, 607, 608

_†Preptoceras_, 202, 203 (restoration), 362, =418=

Primates, 60, =577=; Bridger, 270; Eocene, 577; Santa Cruz, 587; South American, 587; Wasatch, 281, 580

_Priodontes_, 190, 592, 610, 612, 614, 616

_†Proadinotherium_, 262, 462

_†Proasmodeus_, 462

_†Proborhyæna_, 627, =638=

Proboscidea, 60, 230, 254, 264, 269, =422=, 442, 446, 448, 449, 454, 455, 469, 487, 488, 514; African origin of, 234; American, 485; Eocene, 434; Miocene, 234, 238, 430; Oligocene, 432, 441; Pleistocene, N. Amer., 196; Pleisto., S. Amer., 436. (_See also_ Elephants _and_ †Mastodons)

Proboscis, 65

_†Procamelus_, 232 (restoration), 362, =391=, 399 (skull and tooth fig.), 400 (manus fig.), 401 (pes fig.)

_†Procladosictis_, 627

_†Procynodictis_, 517, 529, 530

_Procyon_, 163, 175, 213, 517, =546=, 547; _P. cancrivorus_, 552; _P. lotor_, 153, 166 (fig.), 547 (dentition fig.), 552; _P. †ursinus_, 552

Procyonidæ, 517, 518, =546=; Miocene, 238, 547; South American, 552

_†Prodasypus_, 592

_†Proectocion_, 489

_†Proeutatus_, 592, =614=, 615 (skull fig.)

_†Proglires_, 59

_†Promerycochœrus_, 235, 251, 361, =375=, 376 (restoration)

_†Pronesodon_, 262, 462

Prong Buck, 202, 225, 416, 417, 420. (_See_ Antelope, Prong-horned)

_†Pronomotherium_, 231, 361, =374=, 375 (head restored), 376, 381

_†Propalæohoplophorus_, 243 (restoration), 592, 606 (restor.), =623=

_†Propolymastodon_, 627

_†Propyrotherium_, 462, =487=

_†Prosthennops_, 361

_†Protagriochœrus_, 267, 361, 383, =385=

_†Protapirus_, 257, 291, =323= (skull fig.), 324 (head restored), 325 (teeth fig.)

_†Proteodidelphys_, 627

†Proterothere, single-toed, 506 (restoration); three-toed, 502 (restor.)

†Proterotheres, _see_ †Proterotheriidæ

†Proterotheriidæ, 227, 248, 489, =499=, 507, 653; Araucanian, 227, 508; Deseado, 264, 489; Paraná, 228, 499; Santa Cruz, 248, =501=

_†Proterotherium_, 248, 489, =504=

_†Protheosodon_, 489, =499=

_†Prothoatherium_, 489

_†Prothylacynus_, 243 (restoration), 244, 627, =635=, 636 (restor.), 637

_†Protitanotherium_, 266, 313

_†Protobradys_, 592, 595

_†Protoceras_, 252 (restoration), 258, 362, 405 (restor.), =406= (skull fig.), 407, 445

†Protodonta, 59

_†Protogonodon_, 457

_†Protohippus_, 291, 305 (skull fig.), 306 (manus and pes fig.)

_†Protolabis_, 362, =391=

_†Protomeryx_, 241, 251, 362, 391

_†Protopithecus_, 218

_†Protoreodon_, 267, 361, =380= (skull fig.), 381

Prototheria, =57=, 59, 76

_†Protylopus_, 267, 362, =397=, 399 (skull and tooth fig.), 400 (manus fig.), 401 (pes fig.)

_†Protypotherium_, 243 (restoration), 462, =479=, 480 (restor.)

Province, zoölogical, 145

_†Prozaëdius_, 592

_†Pseudælurus_, 517, =545=

_†Pseudocladosictis_, 627

_†Pseudolabis_, 362

_†Pseudolestodon_, 592

_†Pterodon_, 253, 555, =565= (teeth fig.), 566 (do.), 567, 576

_†Ptilodus_, 627, 642 (skull fig.), 643 (head restored)

Pudu, 180

_Pudua_, 180

Puerco age and stage, 17, 99, 101, 454, 460, 561

Puma, 168 (fig.), 212, 544 (dentition fig.), 545 (skull fig.); South American, 552

Pumas, 153, 163, 176; Pleistocene, 204

Pyramidal, 83

Pyrenees, 104

†Pyrotheres, _see_ †Pyrotheria

†Pyrotheria, 60, 462, =485=, 500; Casa Mayor, 283, 488; Deseado, 262, 485

_†Pyrotherium_, 264, 462, =485=, 486 (head restored)

Pyrotherium Beds, 20, 117, 261, 486

Quadrumana, 582

Quadruped, 1

Quaggas, 292

Quaternary period, 15, 17, 61, 100, =129=, 267, 319; South America, 19

Quicksands, burial of mammals in, 37

Rabbit, 218

Rabbits, 59, 141, 142, 164, 245; White River, 254

Raccoon, 153, 162, 163, 166 (fig.), 175, 547 (dentition fig.), 553; Crab-eating, 552

Raccoon-family, Miocene, 238; Pliocene, S. Amer., 226

Raccoons, 5, 90, 213, 517, 518, 519, =546=, 553; Miocene, 229, 547; Paraná, 227; Pleistocene, 204; Tertiary, 547

Race, geographical, 52

Radius, 80

Raised beaches, 113, 134

Rancho La Brea, 31

_Rangifer_, 70, 152, 157 (fig.), 202, 208, 362, 412

Ratel, 551

Rats, 60, 245; fish-eating, 182; Pleisto., S. Amer., 218; spiny, 184

Rattlesnake stage, 127

RAY. J., 51

Realm, zoölogical, 145

Recent epoch, 17, 132, 335, 336; South American, 19

Reduction of parts, 656

Region, zoölogical, 145

Reindeer, 70, 141, 412; Lapland, 152; Pleistocene, 27

Reptiles, _see_ Reptilia

Reptilia, 55; as ancestral to mammals, 643; distribution, 141; Mesozoic, 284; Oligocene, 117; Paleocene, 284; Santa Cruz, 244; teeth of, 92; Triassic of S. Africa, 644

Republican River age, 17, =127=

Restorations, how made, 42

_Rheithrodon_, 182

Rhinoceros, 350, 490, 492; African, =327=, 328, 329, 337; †aquatic, 347 (restoration); Bornean, 44; Broad-lipped, =329=, 351, 448; †cursorial, 252 (restor.), 341 (do.), 343 (manus fig.), 344 (restor.); †hornless, 252 (restor.), 256 (do.), 335 (skull fig.); Indian, 44, 327, 328, 329; Javan, 327, 328 (skull fig.), 473; †paired-horned, 239 (restor.); †primitive, 271 (restor.); †small-horned, 230 (restor.); Sumatran, 327, 329; White, 329; †Woolly, 332

_Rhinoceros_, 327; _R. sondaicus_, 327, 328 (skull fig.), 473; _R. unicornis_, 329

Rhinoceroses, 45, 56, 60, 63, 91, 289, 312, 382, 461, 510, 654, 655, 661; African, 346; †aquatic, 291, =340=; †aquatic, Bridger, 272; †aquatic, Uinta, 348; †aquatic, White River, 346; bones of, 35; †cursorial, 291, =340=; †cursorial, Bridger, 272, 343; †cursorial, Uinta, 266; †cursorial, White River, 255, =340=; †cursorial, Wind River, 275; Eocene, 338, 339; hairy, 448; John Day, 250, 256, 333; Miocene, 230, 234, 238, 256, 332, 333; North American, 39, 199; Oligocene, 333; Pliocene, 224, 331; †paired-horned, 256, 444; phyla of, 289, 650; Siberian, 39; true, 291, =326=, 340, 346, 350, 351; true, Uinta, 266; true, White River, 255, 333; White River, 255, 333

Rhinocerotidæ, 291, =326=, 340, 350

_†Rhynchippus_, 462

Ribs, 74 (fig.); sternal, 74

Rio de La Plata, 128

River deposits, 36

Robin, 50

Rocky Mts., 101, 150, 153; Pleistocene glaciers, 131

Rodent, †primitive, 271 (restoration); Santa Cruz, 243 (do.)

Rodentia, 5, 59, 282, 283, 284, 459, 629; Araucanian, 226; Boreal, 153; Bridger, 270; Deseado, 587; distribution, 138; John Day, 249; jumping, 90; Miocene, 229, 233, 237; Neotropical, 183 (figs.); Paraná, 227; Pleistocene, 134, 205; Pleisto., S. Amer., 218; Pliocene, 222; Santa Cruz, 245; simplicidentate, 628; Sonoran, 163; South American, 181; Uinta, 265; Wasatch, 280; White River, 254; Wind River, 275; West Indian, 191

Rodents, _see_ Rodentia

Roots of teeth, 95

Rootless teeth, 96

Rosebud stage, 120, 235

Ruminants, 81, 84, 87, 281, 373, 651; hollow-horned, 328; Miocene, 232; true, 54, 201, 362, 387, 402, =409=, 446

RUSSELL, I. C., 589

Sables, 141

†Sabre-tooth, 32; cat, 252 (restoration); cats, 659; false, 542 (skull fig.); primitive, 539 (restor.); Tiger, frontispiece (restor.), 195 (restor.), 517, 531 (skull fig.), 534 (do.), 536 (restor.); tigers, 54, 210, =530=, 552; Miocene, 229, 234, 534; Oligocene, 535; Pleistocene, 204; Pleisto., S. Amer., 211; Pliocene, 223

†Sabre-tooths, 265, 650; false, 249, 541; John Day, 249, 535, 541, 542; Miocene, 238; White River, 254. (_See also_ †Machairodontinæ)

Sacramento Valley, Miocene, 118

Sacrum, 73 (fig.)

_†Sadypus_, 592

Sagittal crest, 63

_Saiga_, 65

Saiga Antelope, 65

St. Elias Alps, 101

St. Lawrence Valley, invasion of, by sea, 133

Sakis, 578, =585=

Saline water, 34

SALISBURY, R. D., 130

Salt Lake, Utah, 131

Salt lakes, 24

Sand, wind-blown, 33

Santa Cruz age and stage, 20, 30, =124=, 262, 263, 264, 282, 283, 467, 470, 473, 474, 475, 477, 479, 481, 482, 485, 493, 499, 500, 501, 504, 508-512, 586, 587; mammals, 243 (restorations)

Santa Cruz Mts., Calif., 118

Santa Cruz River, as barrier to armadillos, 139

Sapajou, 584 (fig.)

_Sarcophilus_, 634

SARMIENTO, 143

_†Scalibrinitherium_, 489, =493=, 495, 496 (skull fig.), 497 (do.)

_Scalops_, 163

Scalpriform teeth, 96 (fig.)

_Scapanus_, 163

Scaphoid, 83

Scapho-lunar, 83

Scapula, 76 (fig.)

_†Scelidotherium_, 592, 601, =602=, 604

_†Schismotherium_, 592

_†Schizotherium_, 291, 357

SCHLOSSER, M., 262, 380, 514, 555, 583, 625, 661

SCHUCHERT, C., 105, 114, 119, 126

_†Sciuravus_, 280

Sciuromorpha, 270

_Sciuropterus_, 164

_Sciurus_, 164 (fig.)

_†Sclerocalyptus_, 219, 592, =618=, 620

_Scleropleura_, 592, =611=

SCOTT, D. H., 288

Sea-Cow, 60, 207, 442

Sea-Otter, 517, 518

Seals, 1, 2, 3, 37, 56, 59; Pleistocene, 132

Seas, barriers to land mammals, 139

Section, geological, 7, 9 (diagram)

Sedimentary rocks, 6

Sediments, 6

Selenodont tooth, 360 (fig.); origin of, 651

Sewellel, 153, 233

Sewellels, 249; Miocene, 238

Shales, Florissant, 129; Green River, 109

Sheep, 54, 60, 93, 362, 409, 416, 418, =419=, 420; Rocky Mt., 152, 419

Shells, fossil, 662

Sheridan stage, 33, =131=, 133, 200

Shrews, 59, 141, 173, 191; American, 163; jumping, 59; Old World, 152; tree, 59

Siberia, 197, 207, 332, 350, 426; frozen carcasses in, 39

Sierra Nevada, 101, 122, 150, 153; Miocene, 118; Pleistocene glaciers, 131

_Sigmodon_, 163

Silurian period, 15

Simiidæ, 583

Simplicidentata, 60

SINCLAIR, W. J., 107, 437

_†Sinopa_, 565 (teeth fig.), 566 (do.), 633

Sirenia, 60, =442=

_Sitomys_, 153, 164, 182

Skeleton, 61; significance of, 42

Skull, 61

Skunk, 163, 167 (fig.), 213, 517; Argentine, 174 (fig.); Little, 174 (fig.); Spotted, 517

Skunks, 153, 163, 174, 210, 518, 550, 551; Pleistocene, 204; South American, 552

Sloth, Three-toed, 186 (fig.), 591; Two-toed, 74, 187 (fig.), 591

Sloths, 2, 60, 97, 186, 189, 592; Araucanian, 226; Pleistocene, 218; Santa Cruz, 245

_†Smilodon_, frontispiece (restoration), 195 (do.), 204, 211, 517, =531= (skull fig.), 532 (teeth fig.), 535, 536, 537, 544, 553, 622

SMITH, PERRIN, 23

SMITH, WILLIAM, 7, 9

Smith River stage, 121

Snake Creek age and stage, 17, =127=, 222, 388

Snakes, 244; Paleocene, 284

_Solenodon_, 173 (fig.)

Solitary species, 38

Sonoran region, 146, 147 (map), 152, 153, 161, 176, 178, 191, 363

_Sorex_, 152

South Africa, 14; Permian glaciation, 25; Triassic reptiles, 644

South America, Eocene separation from N. Amer., 104; Miocene junction with N. Amer., 120; Permian glaciation, 25; Pleistocene Man, 589; zoölogical divisions, 173 (map); zoölogy, 146

South Australia, dry lakes of, 34

South Shetland Islands, 124

Sparnacian stage, 108

Species, definition, 51; distribution, 136; origin, 20

Specific area, 136

_Spermophilus_, 163 (fig.), 164

_†Sphenophalus_, 362

_Spilogale_, 174 (fig.), 517, 552

Spiny rats, Pleistocene, 218

Sports, 660

Squirrel, Grey, 164 (fig.); suborder, 270

Squirrels, 2, 60, 245; flying, 164; John Day, 249; Miocene, 229, 238; true, 164, 181; White River, 254

Stag, 358; European, 151; Thian Shan, 151

†Stag-Moose, 195 (restoration), 208, 209 (restor.), =413=

Stage, geological, 15

Stalagmite, 30

Stations, 136

_†Stegodon_, 430, 439

†Stegodonts, 438

_†Stegotherium_, 243 (restoration), 480 (do.), 592, =614=, 615 (skull fig.)

_†Stenomylus_, 241, 242 (restoration), 362, =393=, 408

_Sternum_, 75 (fig.)

_†Stibarus_, 361

STIRLING, E. C., 34, 35

Straits, of Lombok, 135; of Magellan, 143

Stratified rocks, 6

Stream-channels, White River, 113

_†Stylinodon_, 274

_†Stypolophus_, 555

Subregion, zoölogical, 145

Subsidences, Pleistocene, 132

Subungulata, 514

Suillines, 661

Suina, 54, 60, 361, =362=

Sumatra, 21, 140, 327

Superposition of beds, 7, 8 (diagram)

_Sus_, 359 (fore-arm bones fig.), 363

Swamps, burial of mammals in, 33

Swan, 70

Swine, 54, 60; American, 363; Old World, 363, 364; Pleistocene, 201; true, 364, 365. (_See also_ Peccaries)

Swine-like animals, 361, =362=

Sycamores, 102

_†Symbos_, 208, 362, =418=

_Synaptomys_, 153

_†Syndyoceras_, 241, 258, 362, 403 (restoration), =404=, 406, 407

Syria, 481

_†Systemodon_, 280, 291, =324=

_†Tæniodontia_, 60, 276, =625=; Bridger, 267; Puerco, 286; Wind River, 274

_Tagassu_, 161, 177 (fig.), 178, 360 (tooth fig.), 361, 363 (dentition fig.), 364

Tagassuidæ, 361, =363=

Takin, 418

†Taligrada, 443

_Tamandua_, 187, 188 (fig.), 591

_Tamias_, 153

Tapir, 47 (fig. of young), 81 (fore-arm bones fig.), 87 (leg-bones fig.), 289 (manus fig.), 290 (pes fig.), 320 (adult fig.), =321= (skull fig.), 471, 490, 492; Asiatic, 321; Pinchaque, 322; White River, 323 (skull fig.), 324 (head restored)

_†Tapiravus_, 291

Tapiridæ, 60, 65, 89, 141, 176, 289, 291, 312, 315, =319=, 330, 341, 348, 359, 461, 651, 653; American, 322; Bridger, 272; distribution, 137; Eocene, 323; John Day, 250; Miocene, 231, 234, 322; North American, 39; Oligocene, 323, 339; Pleistocene, 199, 201, 208, 210, 322; Pleisto., S. Amer., 213, 215; Pliocene, 223, 322; South American, 324; Uinta, 266; Wasatch, 280, 324; White River, 257, 322

Tapiroid, 272, 315

Tapiroids, 321

Tapirs, _see_ Tapiridæ

_Tapirus_, 176, 291; _T. †haysii_, 201, 322; _T. roulini_, 322; _T. terrestris_, 47 (young fig.), 87, 201, 289 (manus fig.), 290 (pes fig.), 320 (adult fig.), =321= (skull fig.), 322, 325 (upper teeth fig.)

Tardigrada, 186, 591, 592, 610; Araucanian, 226. (_See also_ Sloths)

Tarija Valley, Pliocene, 129, 225

Tar-pools, 31; Pleistocene, 32

Tarsier, 281, =580=

Tarsiids, 583

_Tarsius_, 281, =580=

Tarsus, 88

Tasmania, 138, 632, 634

Tasmanian Devil, 627, =634=; Wolf, 43, 226, 244, 626, =632=, 633 (fig.)

_Tatu_, 160, 190 (fig.), 592, 593, 612

_Taurotragus_, 202

_Taxidea_, 153, 162, 168 (fig.), 517

_Tayra_, 175 (fig.), 213, 517, 552

Teeth, 92; importance of fossil, 38

_†Teleoceras_, 291, =331=, 332, 333, 350

_†Telmatherium_, 291

_†Temnocyon_, 517, =528=, 530

Temperature as a barrier to species, 140, 141

Tenrecs, 173

_†Tephrocyon_, 517, 522, =527=, 530

Tertiary period, 15, 17, 19, =99=, 267, 319, 369, 413, 460, 531; Central America, 22; Culebra, 22; Great Plains, 36; Patagonia, 20; South America, 20, 248, 461, 463; Tierra del Fuego, 20

Terrestrial habit, 2

_†Tetrabelodon_, 430, 437

_Thalarctus_, 148 (fig.)

_†Theosodon_, 243 (restoration), 248, 489, =493=, 494 (restor.), 496 (skull fig.), 497 (do.), 498 (manus fig.)

Thian Shan, 419

_†Thinohyus_, 361

_†Thoatherium_, 243 (restoration), 248, 489, 500, 501, =504=, 505 (skull fig.), 506 (restor.), 507 (pes fig.)

_†Thomashuxleya_, 462, 485

_Thomomys_, 164

Thorax, 74

Thousand Creek age and stage, 17, 127

Thylacine, 43, =632=, 633 (fig.), 634, 635. (_See also_ Tasmanian Wolf)

Thylacynidæ, 627, =632=

_Thylacynus_, 43, 226, 244, =632=, 633 (fig.)

Tibet, 224, 418

Tibia, 86, 87 (fig.)

Tierra del Fuego, 20, 178

Tiger, 45

†Tillodontia, 59, 276; Bridger, 267; Wasatch, 276; Wind River, 274

Time, geological, 16

†Titanothere, 253 (restoration), 271 (do.), 309 (do.), 314 (restor. and fig. of molar)

†Titanotheriidæ, 291, =308=, 317 (heads restored), 334, 352, 353, 357, 366, 445, 446, 458, 465, 654, 661; Bridger, 270, =313=; Oligocene, =310=, 314, 315, 339; Uinta, 266, 313; White River, 255, =310=, 313, 315; Wind River, 275, 276, 315

_†Titanotherium_, 253 (restoration), 291, 309 (restor.), 310 (molar fig.), 311 (skull fig.), 317 (head restored), 318 (fig. of manus)

_Tolypeutes_, 189, 592, 611, 616

Toronto, interglacial beds near, 130

Torrejon age and stage, 17, 99, =101=, 286, 453, 561

Tortoises, 244; Paleocene, 244

_†Toxodon_, 212 (restoration), 215, 217 (restor.), 462, =463=, 466 (skull fig.), 467, 468, 469, 471, 472 (pes fig.), 473, 477, 487

†Toxodont, 498; horned, 228 (head restored), 263 (do.); Pampean, 212 (restoration), 217 (do.); Santa Cruz, 243 (restor.), 467 (skull fig.); Santa Cruz horned, 474 (restor.)

†Toxodonta, 60, 282, 462, =463=, 477, 482, 483, 487, 500, 509, 511, 652; Araucanian, 227; Deseado, 262, 264, =474=; Paraná, 228; Santa Cruz, 246, =467=

†Toxodontia, 60, 355, =461=, 478, 485, 489, 492, 500, 514; Pleistocene, 215, 221

†Toxodontidæ, 462, 474

†Toxodonts, _see_ †Toxodonta

Tragulina, 54, 60, 408, 409, 410. (_See_ Mouse-Deer)

Transition zone, 147 (map), 153

Trapezium, 83

Trapezoid, 83

Tree-sloths, 591, 593, 594, 595, 596, 609; Pleistocene, 596; Santa Cruz, 596. (_See also_ Sloths)

_Tremarctos_, 172, 176 (fig.), 517, 548, 552

Trèves, 10

Triassic period, 15, 16, 642, 643; climate, 24

†Triconodonta, 59

Trier, cathedral of, 10

_†Trigodon_, 227, 228 (head restored), 462, =466=, 473, 474

_†Trigonias_, 256, 291, =336=, 337 (skull and front teeth fig.), 338, 339 (manus fig.), 351

_†Trigonolestes_, 281, 361, =398=

†Trigonolestidæ, 361

†Trigonostylopidæ, 509, 512

_†Trigonostylops_, 509

_†Triisodon_, 554, =561=

_†Trilophodon_, 229

Trinidad, 170

Trinomial system of nomenclature, 52

_†Triplopus_, 266, 272, =343= (manus fig.), 345

_†Tritemnodon_, 271 (restoration), 555, 565 (teeth fig.), 566 (do.), =567= (restor.), 576, 633

†Trituberculata, 59

Tropical species, distribution, 141

Tse-tse Fly, 142

Tuatara, 284

Tubulidentata, 60

Tuco-tuco, 184

Tuff, Miocene, 112, 122; Santa Cruz, 124

Turkestan, 419

Turtles, 102

Tusks, 92

Tylopoda, 54, 60, 362, =386=, 409, 410; Pleistocene, 202

†Typothere, 243 (restoration), 480 (do.), 636 (do.), 639 (do.)

†Typotheres, _see_ †Typotheria

†Typotheria, 60, 215, 372, 462, =476=; Araucanian, 227; Casa Mayor, 282, 479; Deseado, 263, 264; Paraná, 228; Pleistocene, 215, 221, 476; Santa Cruz, 246, =479=; Tertiary, 215

†Typotheriidæ, 462, =476=

_†Typotherium_, 215, 217, 263, 462, =476=, 477

Uakaris, 578, =585=

Uinta age and stage, 11, 17, =110=, 270, 271, 272, 301, 339, 345, 349, 365, 369, 370, 380, 383, 385, 386, 397-400, 409, 443, 519, 527, 529, 557, 559, 573, 579

Uinta Mts., 106, 108; Pleistocene glaciers, 131

_†Uintacyon_, 555, 558

†Uintatheres, _see_ †Uintatheriidæ

†Uintatheriidæ, 285, =443=, 444, 445 (skull fig.), 451, 452, 454, 465, 509, 532; Bridger, 269, 443; Wasatch, 279, 451; Wind River, 274, 450

_†Uintatherium_, 51, 271 (restoration), 443, =444=, 445 (skull fig.), 447 (restoration)

Ulna, 80

Unciform, 83

Unconformity, 312

Ungual phalanx, 84

Ungulata, 60, =513=, =516=; primitive, 460; Santa Cruz, 481, 511; †short-footed, 443; South American indigenous, 461, 466, 469, 486, 489, 490, 500, 509, 511, 513, 514; White River, 258

Ungulates, _see_ Ungulata

Unguligrade, 91

University of California, 31, 32

Upheavals, Pleistocene, 132, 133; Pliocene, 132

Upper Sonoran zone, 148, 164

Ural, Mts., 106; Sea, 106, 108

_Urocyon_, 162, 165 (fig.), 517

_†Urotrichus_, 153

Ursidæ, 517, 518, =548=

_Ursus_, 90 (pes fig.), 156 (fig.), 163, 517, 549

Uruguay, 585

Variant, 53

Varieties, 52, =662=

Vegetation, Eocene, 111; Paleocene, 283. (_See also_ Flora _and_ Plants)

Vermilingua, 187, 591

Vertebra, 68; caudal, 73 (fig.); cervical, 70 (fig.); dorsal, 69 (fig.), 72 (fig.); lumbar, 72, 73 (fig.); sacral, 73 (fig.); thoracic, 69

Vertebral column, 67

Vertebrata, 55

Vesuvius, 30

Vicuña, 178 (fig.)

Virgin Valley stage, 127

_Viscaccia_, 183 (fig.), 185

_†Viverravus_, 555, =558=

Viverridæ, 518, 553, 554, 558

Viverrines, _see_ Viverridæ

Viviparous mammals, 59

Vizcacha, 183 (fig.), 185

Vizcachas, Pleistocene, 218

Volcanic ash, 29; Bridger, 110, 115; John Day, 116; Santa Cruz, 124; White River, 115

Volcanic dust, 29

Volcanic material, 6; Florissant, 121; Miocene, 118; Pliocene, 125

Volcanoes, 133

Voles, 182

VOLTAIRE, 646

Vulcanism, Miocene, 118, 121; Pliocene, 127

_†Vulpavus_, 555, 558

_Vulpes_, 149 (fig.), 150 (fig.), 158 (fig.), 517

WAAGEN, W., 662

WALLACE, A. R., 136, 139, 150, 170, 171

Walnuts, 102

Walruses, 1, 45, 207, 210, 516; Pleistocene, 27, 132

Wapiti, 50, 151, 155 (fig.), 181, 202, 208, 411, 412, 413

Warm Temperate region, 161

Wart Hog, 363

Wasatch age and stage, 17, =106=, 273, 274, 275, 285, 316, 325, 370, 398, 400, 451, 452, 453, 455, 457, 459, 560, 561, 566, 568, 571, 572, 580, 581

Wasatch Mts., Pleistocene glaciers, 131

Wasatch-Sparnacian stage, 115

Water Hog, 183 (fig.), 185, 205, 211. (_See also_ Capybara _and_ Carpincho)

Weasel, 551; family, 174; Miocene, 238; Pleisto., S. Amer., 213; tribe, 518

Weasels, 59, 152, 517; Miocene, 229, 238; Pleistocene, 204, 205

WEBER, M., 426

Western Hemisphere, marsupials, 626

West Indian, islands, 164, 191; shells on N. J. coast, 113; subregion, 170 (map)

West Indies, 583; Eocene, 112; Oligocene, 113; Paleocene, 103; Pleistocene, 134; zoölogy, 146

Whale, Right, 48

Whales, 1, 2, 3, 37, 45, 60, 74, 442; Miocene, 123; Pleistocene, 132; toothed, 60; whalebone, 60, 94

White Mts., Labrador plants of, 193

White River age and stage, 11, 12, 17, =113=, 250, 266, 267, 270, 271, 272, 312, 325, 326, 340, 341, 346, 350, 357, 365-371, 375, 377-380, 382-385, 394-396, 399, 405, 407, 408, 523, 528-530, 535, 538-541, 546, 557, 562, 563, 565, 566, 631; mammals, 252 (restorations)

Wild-cats, 141

Willamette Valley, Miocene, 115

WILLISTON, S. W., 33, 589

Willows, 102

Wind River age and stage, 17, =109=, 273, 315, 316, 326, 339, 350, 400, 450, 452, 456, 457, 460, 568, 571

Windward Islands, Pleistocene, 134

Winter, destruction of mammals by, 36

Wisent, 152

Wolf, 32, 62 (skull fig.), 64 (do.), 69 (dorsal vertebra fig.), 70 (atlas fig.), 71 (axis fig.), 72 (cervical and dorsal vertebræ fig.), 73 (lumbar and caudal fig.), 74 (ribs fig.), 75 (ribs and sternum fig.), 76 (scapula fig.), 77 (hip-bone fig.), 78 (humerus fig.), 80 (fore-arm bones fig.), 82 (manus fig.), 85 (femur fig.), 86 (femur and patella fig.), 87 (leg-bones fig.), 88 (pes fig.), 92, 93 (dentition fig.); Fox-like, 171 (fig.); Grey, 152, 159 (fig.); Large-eared, 656; Miocene, 522 (skull fig.); Timber, 159 (fig.), 162

Wolverene, 141, 152, 155 (fig.), 213, 238, 517, 551; Pleistocene, 204

Wolves, 59, 164, 173, 249, 517, 518, 520, 523, 525, 530; fox-like, 173, 212, 552; Pleistocene, 204; Pliocene, 222; White River, 254

Wombats, 640

Woodchuck, 152 (fig.), 153

Wood-rats, 141, 153, 164

WORTMAN, J. L., 383, 385, 399, 570, 571

_†Xotodon_, 462

Yapock, 631

Yellowstone Park, petrified forests, 122; Miocene lava, 122; Pliocene lava, 127

Young animals, colour pattern of, 46

Yucatan, 128

Yukon Valley, Miocene, 118

_Zaëdyus_, 190, 592

_Zapus_, 153, 160 (fig.)

Zebra, 44; bones of, 35; Burchell’s, 200

Zebras, 213, 292, 308

†Zeuglodontia, 60

ZITTEL, K. VON, 601

Zoölogy, Experimental, 648, 663

_†Zygolestes_, 627, 641

Zygomatic arch, 65

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=New York, 1907= =New Edition, completely revised, 1907= =Latest Reprint, 1909=

_Illustrated_ _12mo_ _$2.60_

Intended to serve as an introduction to the science of Geology, both for students who desire to pursue the subject exhaustively and also for those who wish merely to obtain an outline of the methods and principal results of the science. To the future specialist such a preliminary survey of the whole field will afford the necessary orientation. To the non-specialist the graphic presentation of the outlines of the subject cannot fail to prove both interesting and informing. The book aims to cultivate a proper scientific attitude by training the student to carefully distinguish between fact and inference and between observation and hypothesis. He is taught to weigh his evidences carefully, and while balancing probabilities suspend judgment where the data for decision are insufficient.

The new edition incorporates the results of all the important advances made in geological knowledge in recent years. The number of illustrations has been greatly increased, thus adding to the admirable clearness of the text.

Guide to the Study of Animal Ecology

BY CHARLES C. ADAMS

Associate in Animal Ecology in the University of Illinois

_Cloth, 12mo_ _183 pp._ _$1.25 net_

This work is the outgrowth of the author’s efforts during the last ten years to find some consistent and satisfactory working plan for handling the almost bewildering number of facts of ecological significance which have been accumulating in the literature of zoölogy, biology, and the allied sciences. An ecological point of view is described more fully than other subjects, so that the student may see the need of familiarity with those tests or criteria by means of which he may be able to determine for himself ecological relations and the validity of ecological studies. The other phases are treated less fully in the discussions and with more detail bibliographically, so that this may be a useful source-book. In fact, the very extensive and up-to-date bibliography is one of the important features of the entire book.

The Age of Mammals in Europe, Asia, and North America

BY HENRY FAIRFIELD OSBORN

A.B., SC.D. PRINCETON, HON. LL.D. TRINITY, PRINCETON, COLUMBIA, HON. D.SC. CAMBRIDGE UNIVERSITY, HON. PH.D. UNIVERSITY OF CHRISTIANIA, PRESIDENT AMERICAN MUSEUM OF NATURAL HISTORY, PRESIDENT NEW YORK ZOÖLOGICAL SOCIETY

=ILLUSTRATED BY 232 HALF-TONE AND OTHER FIGURES, INCLUDING NUMEROUS MAPS, GEOLOGICAL SECTIONS, FIELD VIEWS, AND REPRODUCTIONS FROM PHOTOGRAPHS OF MOUNTED FOSSIL SKELETONS AND OF THE FAMOUS RESTORATIONS BY CHARLES R. KNIGHT.=

_Royal 8vo_ _$4.50 net_ _Carriage extra_

“The Age of Mammals” is not written for the palæontologist only. No zoölogist interested in mammals, birds, fishes, or reptiles can fail to find it of value. The geologist finds here the clearest exposition that has been given of the succession of geological events in the mammal-bearing continental formations of the Tertiary and Quaternary of the Western States. The anthropologist finds in the closing chapter on the Pleistocene a key to most of the problems which confront him as to the time of man’s first appearance. The botanist may refer to it for the succession and evolution of flora.

To the general reader it offers the first connected account of the history of life on the earth during the later geological epochs, a record embodying the very latest results of the active research going on in this direction at the present time. In so far as science has succeeded in piecing together the fragmentary evidence of the rocks, this volume contains glimpses into the remote past of the continental outlines, the climate, vegetation, and animal life of the epochs preceding the “Age of Man.” The text is supplemented by a very original and suggestive series of illustrations, notable among which are numerous half-tone reproductions from the famous restorations of extinct mammals by Charles R. Knight, many of which are published here for the first time. Moreover, there is appended to the volume an invaluable Classification of the Mammalia, which gives not only the systematic position but also the geologic and geographic distribution and the popular names of all the important genera of mammals, both living and fossil.

Comments on The Age of Mammals

“Students of palæontology have awaited impatiently the past few years a promised work on extinct mammals by Professor Osborn. In his ‘Age of Mammals,’ expectations have been more than realized.”—S. W. WILLISTON, in _Science_, Feb. 17, 1911.

“Dr. H. F. Osborn is a great palæontologist; in this book he has gathered together the work of a life-time, and that work, besides being original and constructive, is also critical and selective. The result is a great book.” “While it is an incomparable text-book, a work of reference to the student, and, no doubt a fruitful field for the controversialist of the future, it is a work which can be read with interest and satisfaction by the ‘genial omnivore,’ as Huxley called him, the general reader.”—_The Field_, Jan. 7, 1911.

“It is in the best sense a source book, for it gives at first hand, from the original material, the ideas of an acknowledged master in mammalian palæontology.” “It has the clarity and directness of style so welcome, and rare, in such a book.”—E. C. CASE, in _Bulletin American Geographical Society_, July, 1911.

“A book of the utmost value to the student and teacher of mammalian life and likewise to the serious reader.”—_American Journal of Science_, Feb., 1911.

“M. Osborn ... devait s’attacher a nous présenter le tableau aussi complet et aussi fidèle que possible des faunes de Mammifères fossiles qui se sont succédé dans l’hémisphère Nord pendant l’ère tertiaire. Et j’ai plaisir à dire tout de suite qu’il y a parfaitement réussi.”—M. BOULE, in _Mouvement Scientifique_, 1911, p. 569.

“Professor Osborn has produced a book which will appeal to the learned specialist and to the thoughtful general reader as well.” “The work is well adapted to school and college use, and is abundantly illustrated.”—_Education_, Boston, Jan., 1911.

“One of the most notable books on evolution since the appearance of Darwin’s ‘Origin of Species.’”—_Forest and Stream_, Dec. 10, 1910.

“Nejlepší současný palæontolog americký, Henry Fairfield Osborn, vydal nedàvno s titulem tuto citovaným znamenitě psanou a pěkně vypravenou knihu o ‘věku ssavců.’”—F. Bayer in _Věstníku Ceské Akademie císaře Františka Josefa pro vědy, slovenost a umení_.—Ročník XX, 1911.

“Written with clearness and vivacity, most admirably illustrated, especially by the ‘restorations’ of Mr. Knight, and illuminated by maps, Professor Osborn builds, page after page, his story-mosaic.... The reader will soon discover that he is a brilliant generalizer, possessed of material gathered from all around the globe, fructifying his knowledge by the exercise of a constructive imagination, and expressing his facts and ideas in a literary style, clear, vigorous, and entertaining.”—_The Literary Digest_, Feb. 4, 1911.

The Cambridge Natural History

EDITED BY

S. F. HARMER, Sc.D., F.R.S.

Fellow of King’s College, Cambridge; formerly Superintendent of the University Museum of Zoölogy; Keeper of the Department of Zoölogy in the British Museum (Natural History)

AND

A. E. SHIPLEY, M.A., HON. Sc.D., Princeton, F.R.S.

Master and Fellow of Christ’s College, Cambridge; formerly Reader in Zoölogy in the University; Chairman of Council of Marine Biological Association

_In Ten Volumes_ _Fully Illustrated_ _Medium 8vo_ _Gilt Tops_ _Each Volume, $4.75 net_

=CONTENTS=

VOL. I. Protozoa, by M. Hartog; Porifera, by Igerna Sollas; Coelenterata and Ctenophora, by S. J. Hickson; Echinodermata, by E. W. MacBride.

VOL. II. Flatworms and Mesozoa, by F. W. Gamble; Nemertines, by L. Sheldon; Threadworms and Sagitta, by A. E. Shipley; Rotifers, by M. Hartog; Polychaet Worms, by W. B. Benham; Earthworms and Leeches, by F. E. Beddard; Gephyrea, etc., by A. E. Shipley; Polyzoa, by S. F. Harmer.

VOL. III. Molluscs, by H. A. Cooke; Recent Brachiopods, by A. E. Shipley; Fossil Brachiopods, by F. R. C. Reed.

VOL. IV. Spiders, Mites, Scorpions, etc., by C. Warburton; Trilobites, etc., by M. Laurie; Pycnogonids, by D’Arcy W. Thompson; Lingulatulidæ and Tardigrada, by A. E. Shipley; Crustacea, by Geoffrey Smith.

VOL. V. Peripatus, by A. Sedgwick; Myriopods, by F. G. Sinclair; Insects, Part I, by D. Sharp.

VOL. VI. Insects, Part II, by D. Sharp.

VOL. VII. Hemichordata, by S. F. Harmer; Ascidians and Amphioxus, by W. A. Herdman; Fishes (exclusive of systematic account of Teleostei), by T. W. Bridge; Fishes (systematic account of Peleostei), by G. A. Boulanger.

VOL. VIII. Amphibia and Reptiles, by Hans Gadow.

VOL. IX. Birds, by A. H. Evans.

VOL. X. Mammalia, by F. E. Beddard.

WHAT THE CRITICS SAY OF THE CAMBRIDGE NATURAL HISTORY

New York _Evening Post_.

Its editors may well be congratulated upon the completion of such an undertaking, whose vastness and difficulty can be adequately appreciated only by the skilled zoölogist. The student of biology who turns to this volume (Vol. iv) will not be disappointed in its value as a serviceable handbook. It is pleasant to observe how numerous, clear, and satisfactory are the drawings that illustrate the text.

_American Journal of Science._

The most convenient and generally useful work of reference on the subject that has appeared in the English language in recent years.

_Book Review Digest._

The zealous student, anxious to bring his knowledge up to date, will find here a compendium on which he can rely.

_Field._

The Cambridge Natural History series of volumes is one of very great value to all students of biological science.

_Times._

There are very many, not only among educated people who take an interest in science, but even among specialists, who will welcome a work of reasonable compass and handy form containing a trustworthy treatment of the various departments of Natural History by men who are familiar with, and competent to deal with, the latest results of scientific research. Altogether, to judge from this first volume, the Cambridge Natural History promises to fulfil all the expectations that its prospectus holds out.

_Academy._

The editors have aimed very high, and they have succeeded.... Well conceived, carefully coördinated, and executed with the greatest detail and completeness, the Cambridge Natural History is certain to rank high amongst those gigantic scientific works to which, within the last half-century or so, the labours of so many experts, each without hope of more glory than falls to a mere assistant, have contributed.

_Athenæum._

The series certainly ought not to be restricted in its circulation to lecturers and students only; and, if the forthcoming volumes reach the standard of the one here under notice, the success of the enterprise should be assured.

_Science Gossip._

Every library, school, and college in the country should possess this work, which is of the highest educational value.

_Daily News_ in a Review of Vol. X.

A volume which, for the interest of its contents and for its style and method of treatment, is not only worthy of its predecessors, but may be regarded as one of the most successful of a brilliant series.

_A GREAT EXPLORER’S STORY_

My Life With the Eskimo

BY VILHJÁLMUR STEFÁNSSON

_ILLUSTRATED WITH HALF-TONE REPRODUCTIONS OF PHOTOGRAPHS TAKEN BY THE AUTHOR AND OTHERS_

_Decorated cloth, 8vo_

A fascinating book of description and adventure has been written by the famous traveler and explorer, who has passed years of his life within the Arctic Circle. Mr. Stefánsson has had a vast amount of material from which to draw and he has made his selection wisely. He has lived with the Eskimo for long periods; he knows their language; he has subsisted on their food; he has heard their legends; he has seen them in their daily lives as have few explorers. Consequently his remarks about this primitive and matter-of-fact people are shrewd, true, and frequently amusing. The experiences and tales which he recounts, mirroring the hardships and the inspirations of life in a fearful but wonderful country, compose a work quite the most absorbing on it that has ever been published.