CHAPTER XVIII

PALAEONTOLOGY OF THE BRACHIOPODA

INTRODUCTION--DIVISION I. ECARDINES--EXTERNAL CHARACTERS--INTERNAL CHARACTERS--DIVISION II. TESTICARDINES--EXTERNAL CHARACTERS--INTERNAL CHARACTERS--SYNOPSIS OF FAMILIES--STRATIGRAPHICAL DISTRIBUTION--PHYLOGENY AND ONTOGENY

=Introduction=

The wide distribution and vast abundance of the Brachiopoda throughout the whole series of geological formations make this group of especial importance to the student of the past history of the earth; and the zoologist must always regard the fossil forms with peculiar interest, because they not only largely outnumber the living representatives, but comprise numerous extinct genera, and even families, exhibiting types of structure and characters entirely absent in the modern members of the group. It is a most fortunate circumstance that the excellent state of preservation in which we frequently find them, and the immense amount of material at our disposal, enable us to determine with accuracy and certainty the internal characters of the shells in the great majority of cases. But it is only since the beginning of the present century that our knowledge of the anatomy of the soft parts of the living animal has rendered any tracing of homologies possible. In the case of features in fossil extinct types the interpretation must be to some extent doubtful. Barrande, Clarke, Davidson, Hall, King, Oehlert, Waagen, de Verneuil, and a host of other workers have contributed to the information which we now possess; and their works must be consulted for details of the subject.[428]

Since all Brachiopods are inhabitants of the sea, the geologist at once recognises as a marine deposit any bed which contains their remains. Under favourable conditions they swarmed in the seas of Palaeozoic and Mesozoic times. Beds of limestone are frequently almost entirely composed of their shells, as, for instance, some of the Devonian limestones of Bohemia. Often they give the facies to the fauna and outnumber in species and individuals all the other organisms of the period. The Ungulite Sandstone (Cambrian) of Russia and the Productus Limestone of the Salt Range in India of Carboniferous and Permian age are well-known examples.

Many species seem to have been gregarious in habit; thus _Productus giganteus_ of the Carboniferous Limestone may generally be found in crowded masses, as in some localities in Yorkshire.

The fact that certain species of Brachiopods characterise definite stratigraphical horizons or “zones” gives them occasionally an importance equal to that of Graptolites; for instance, the Ecardinate species _Trematis corona_ marks a set of beds in the Ordovician, and the isolated _Stringocephalus Burtini_ is restricted to the upper part of the Middle Devonian, giving to the limestone on that horizon its distinctive name. It is noteworthy also how certain species affect a sandy and others a calcareous sea-bottom, so that beds of the same age show differences in their Brachiopod fauna owing to a dissimilar lithological composition.

While few of the recent Brachiopods reach a large size, some of the extinct species measure several inches in breadth, but the great _Productus giganteus_ attained the width of even a foot.

The bright colours of the shells of the living animals are not generally preserved amongst the fossil species from the older rocks; yet in a Carboniferous _Terebratula_ we can even now detect the purple bands in some specimens, and a Cretaceous _Rhynchonella_ similarly exhibits its original colour.

The Brachiopoda are evidently a group in its decline, as the geological record shows; but they date back from the earliest known fossiliferous rocks, in which the Ecardinate division is alone represented. As we ascend through the stratigraphical series the number and variety of genera and species belonging to both divisions rapidly increase until in the united Ordovician and Silurian there are nearly 2000 species and about 70 genera. From this point of maximum development down to the present day there is a gradual decrease in numbers.

According to Davidson, at least 17 Upper Tertiary species are still living on our sea-bottoms; and many recent Mediterranean forms occur in the Pliocene rocks of the islands and shores of that sea, and in the Crags of East Anglia.

A brief review of the chief characteristics of fossil Brachiopoda is given below. Those genera which have the greatest zoological or geological importance can alone be noticed owing to the exigencies of space.

I. ECARDINES

=External Characters=

A considerable diversity of external form is met with even in this division, from the limpet-like _Discina_ to the flattened tongue-shaped _Lingula_. The valves have most commonly a smooth external surface with delicate growth-lines; but sometimes pittings (_Trematis_) or radiating ribs (_Crania_) are present, and in a few forms the shell is furnished with spines (_Siphonotreta_), which perhaps serve to anchor it in the soft mud of the sea-bottom. The usual mode of fixation was by means of the pedicle (= peduncle or stalk), which either (1) passed out simply between the posterior gaping portion of the valves (_Lingula_), or (2) lay in a slit in the ventral valve (_Lingulella_), or (3) pierced the substance of the latter valve by a definite foramen (_Discina_). The first-mentioned condition of the pedicle seems the most primitive. Rarely the pedicle was absent, and the shell was attached by the whole surface of the ventral valve (_Crania_, p. 467).

The two valves in the fossil Ecardines were held together by muscular

## action, though in some families (_Trimerellidae_) we see traces of

articulating processes. The “hinge line,” or line along which the valves worked as on a hinge, is in most forms more or less curved. A “hinge area” (_i.e._ that portion of the shell generally smoother than other parts of the valves, more or less triangular in form, and lying between the beaks on one or both sides of the hinge line), is usually absent in the Ecardines.

[Illustration: FIG. 322.--Muscle-scars of _Lingula anatina_. Inner surface of =A=, Pedicle-valve or ventral valve. =B=, Brachial or dorsal valve; _p.s_, parietal scar; _u_, umbonal muscle; _t_, transmedians; _c_, centrals; _a.m.e_, laterals (_a_, anteriors; _m_, middles; _e_, externals).]

[Illustration: FIG. 323.--_Trimerella._ (After Davidson and King.) =A=, Inner surface of pedicle-valve or ventral valve: _a_, pseudo-deltidium; _b_, deltidial slope; _c_, deltidial ridges; _d_, areal borders; _e_, cardinal callosities; _f_, cardinal facet; _g_, lozenge; _i_, umbonal chambers separated by cardinal buttress; _j_, platform; _k_, platform vaults; _l_, median plate; _m_, median scars; _n_, anterior scars; _o_, lateral scars; _p_, post-median scars; _q_, crown crescent; _r_, side or lateral crescent; _s_, end or terminal crescent; _t_, transverse scars; _u_, archlet (vascular sinuses); _w_, sub-cardinal scars; _x_, umbo-lateral scars. =B=, Brachial or dorsal valve: _e_, cardinal sockets; _j_, platform; _k_, platform vaults; _l_, median plate; _m_, median scars; _n_, anterior scars; _q_, crown crescent; _r_, side or lateral crescent; _s_, end or terminal crescent; _t_, transverse scars; _u_, archlet (vascular sinuses); _v_, cardinal scars; _w_, sub-cardinal scars.]

=Internal Characters=

Owing to the rarity of well-preserved interiors of valves in this division, our knowledge of their internal characters is still far from satisfactory. The arrangement of the muscular impressions varies greatly amongst extinct genera, but we are often able to interpret them with a considerable amount of certainty by a study of the scars and the muscles of the well-known recent _Lingula_ (Fig. 322). The extreme specialisation of the muscles in many of the earliest genera (_e.g._ _Lingula_) is remarkable, and points to a long but so far undiscovered ancestry in pre-Cambrian times.[429] In fossil species of _Crania_ and _Lingula_ the muscle-scars correspond closely with those in the living representatives of these genera. In the most highly specialised family of the Ecardines--the _Trimerellidae_--we meet with features of peculiar interest.[430] The muscle-scars in this family (Fig. 323, A, B) are most remarkable for the development of the so-called “crescent,” (_q.r.s._) which skirts the posterior margin of both valves as a sub-cardinal impression. It is believed to be the trace of a strong post-parietal muscular wall, analogous in position to that of _Lingula_. The three pairs of “lateral” muscle-scars in the latter genus seem to be represented by the “terminal” (_s_) and “lateral” (_r_) scars on the crescent of the _Trimerellidae_. A pair of “transverse” scars (_t_) occurs in each valve between the “terminals” and the antero-lateral edge of the “platform” (_j_). “Cardinal” (_v_), “sub-cardinal” (_w_), and “umbo-lateral” (_x_) scars also occur. The median impression which covers the “platform” (_j_) consists of a central, lateral, and usually an anterior pair of scars; and the impressions of the genital organs, according to Davidson and King, lie medianly posterior to the “platform.” The “platform” itself is a more or less conspicuous central calcareous elevated area occurring in each valve, but most developed in the dorsal; in some cases it is double-chambered with tubular cavities (“platform vaults,” Fig. 323, A, B, _k_), in others it is more or less solid. It appears to have originated through a posterior shifting of the central muscular bands, that they might be inserted behind the liver; at the same time a deposition of shelly material, to form fulcra to work the heavy valves, took place at these points. The tunnelling-out of the platform was probably due to the continual pressure of the lobes of the liver. The division of the umbonal cavity into definite chambers in _Monomerella_, and to a less extent in other members of this family, appears, according to Davidson and King, to have been caused by pressure of the ovarian lobes.

In connexion with the foregoing remarks on the development of the “platform,” it may be mentioned that the paths along which the muscle-bands move, as the shell of Brachiopods increases in size, are marked by elongated scars, and often by shelly deposits; and when the members of a muscle-pair come into juxtaposition these shelly deposits (which act as fulcra for the muscles) combine, and by the growth of the shell form a septum, as in the case of the median septum of _Lingulepis_.

The _Obolidae_ show some important features in the internal impressions. _Obolella crassa_ (Hall) may be taken as a well-known type of the family. In this species a pair of small scars, one on each side of the pedicle-groove, lies close under the hinge line in the ventral valve. There is also a well-marked scar for the insertion of the pedicle-muscle at the end of the pedicle-groove. A pair of much elongated lateral impressions extending forward from the “cardinals” may be homologous with the “laterals” of _Lingula_; and the two small central scars between them may be compared with the “centrals” of _Lingula_ which are in a somewhat similar position. In the dorsal valve of _O. crassa_ a pair of “cardinals” is found, and on each side of a low median rounded ridge are two small “central” scars. Indistinct “lateral” scars arise close to or in the central area, and diverge anteriorly.

Sometimes a great concentration of muscle-scars occurs round the foramen in the ventral valve, as in _Siphonotreta_.

As regards the minute structure and composition of the shell in the Ecardines, we find that the _Lingulidae_ and _Discinidae_ have their shell composed of alternating layers of phosphate of lime and a corneous substance; the former layers are pierced by microscopic canals. The _Craniidae_ have calcareous shells traversed by tubules, which divide into many fine branches near the external surface; a thin periostracum covers the exterior. The _Trimerellidae_ have heavy thick calcareous shells, for which they required the previously-described elaborate arrangement of muscles to open and shut them.

II. TESTICARDINES

=External Characters=

It is to this division that the great majority of the Brachiopoda belong; and the diversity of form, of ornamentation, and of internal characters is correspondingly greater than in the Ecardines.

A transversely or longitudinally oval shape of shell is the commonest; but sometimes it is triangular, as in _Rhynchonella_ (Fig. 327), or bilobed, as in _Pygope_ (= _Terebratula diphya_). The ventral valve is usually more convex than the dorsal, and the former may be prolonged into a tube by the accelerated growth and infolding of the anterior and lateral margins, producing a very abnormal form (_Proboscidella_). The external surface of the valves is frequently ornamented with more or less prominent radiating ribs; and fine concentric growth-lines are commonly shown, and may be developed into coarse ridges or wrinkles, particularly in old individuals. The members of the family _Productidae_ are usually furnished with tubular spines, which are sometimes of great length, and served to anchor the free shells in the mud, or were twisted round Crinoid stems and similar objects.

In the ventral valve of many genera there is a median sinus, with a corresponding fold in the dorsal valve, and rarely _vice versâ_; sometimes the fold and sinus are double.

The hinge line is either curved or straight, and the valves are articulated by means of a pair of “hinge-teeth” (Fig. 329, _t_) in the ventral valve, which fit into corresponding sockets in the opposite valve. Some genera have the teeth very rudimentary, or have lost them altogether. The teeth are frequently supported by “dental plates,” and the sockets by “socket plates” (_e.g._ _Conchidium_, Figs. 324, 325). A few genera with a long hinge line have the whole of it denticulated (_Stropheodonta_). In the dorsal valve medianly close under the hinge line is a shelly protuberance--the “cardinal process”--to which the diductor muscles are attached. It is sometimes of great length and forked (_Stringocephalus_, Fig. 326), or tripartite, or even quadripartite; but in _Rhynchonella_ and some other genera it is rudimentary.

[Illustration: FIG. 324.--_Conchidium galeatum._ Wenlock Limestone.]

[Illustration: FIG. 325.--_Conchidium galeatum._ Transverse section. _d_, Dorsal valve; _d.s_, dorsal septum; _s_, socket plate; _v_, ventral valve; _v.s_, ventral septum; _d.p_, dental plate.]

[Illustration: FIG. 326.--_Stringocephalus Burtini._ (Modified from Woodward.) Devonian. =A=, Interior of dorsal valve. =B=, Side view of interior of shell; _a_, adductor (= occlusor) scars; _c_, crura; _c.p_, cardinal process; _d.s_, dorsal septum; _h.p_, hinge plate; _l_, brachial loop; _s.p_, shelly processes; _t.s_, dental sockets; _v.s_, ventral septum.]

A “hinge area” (Fig. 334, _c.a_) is often present on one or both valves, and may be of great size, as in _Clitambonites_, but in _Productus_ it is wholly absent. In those genera that possess it a triangular fissure--the “deltidial fissure”--frequently traverses it on both valves; in the dorsal valve the fissure is merely the space between the dental sockets, and may be occupied by the cardinal- process (Fig. 334, C) or covered by a shelly plate--the “chilidium.” In the ventral valve it gives passage to the pedicle, and may be partly or entirely closed by a similar plate (Fig. 334, _d_) known as the “pseudo-deltidium,” especially large in _Clitambonites_, or remain open (_Orthis_). This pseudo-deltidium is a primitive character, and arises in an early stage of the development as a shell-growth on the dorsal side of the animal, becoming attached to the ventral valve subsequently. The pedicle in many genera passes out through a special foramen in the beak of the ventral valve; and its proximal portion is often embraced by a pair of small plates--the deltidial plates or “deltidium”--which are formed on lateral extensions of the ventral mantle lobe, according to Beecher. These plates lie on each side of the pedicle, or grow round and unite in front of it (_Rhynchonella_, Fig. 327), or constitute merely its anterior border (_Terebratula_, Fig. 328). In some cases this foramen becomes closed in old age.

[Illustration: FIG. 327.--_Rhynchonella Boueti._ (Cornbrash.) _d_, Deltidium; _f_, foramen.]

[Illustration: FIG. 328.--_Terebratula sella._ (Lower Greensand.) _d_, Deltidium; _f_, foramen.]

The dorsal valve in a few cases has its beak perforated by a foramen--the “visceral foramen.” This foramen is in no way connected with the pedicle foramen, but points perhaps to the existence in the early Testicardinate genera of an anal aperture. In _Athyris concentrica_ (Devonian) this foramen is connected internally with a cylindrical tube, which extends longitudinally to about one-third the length of the valve. In _Centronella_ the aperture in the cardinal plate is rounded and complete; and in _Strophomena_ and its allies the opening lies between the cardinal processes. If this feature is correctly interpreted, it suggests a retrogression of the group since Palaeozoic times not only in numbers, but in structure; and other evidence points the same way.

=Internal Characters=

The interior of the shell is sometimes more or less divided up by septa. A median septum occurs in one or both valves of many genera as a low ridge or strongly developed partition (_Waldheimia_, Fig. 329, _ss_; and Stringocephalus, Fig. 326, B, _v.s_). _Conchidium_ (Fig. 325) has its dental plates of great size, and uniting to form a V-shaped chamber or “spondylium,” supported by a median double septum; and by means of these with a pair of septa and the large socket-plates in the dorsal valve the interior of the shell of this genus is divided up into several chambers.

The interiors of several other genera are somewhat similarly divided up.

[Illustration: FIG. 329.--_Waldheimia (Magellania) flavescens._ =A=, Interior of ventral valve: _a_, adductor scars; _v.a_, ventral adjustors; _d_, divaricators; _a.d_, accessory divaricators; _p_, peduncular muscle; _dm_, deltidium; _f_, foramen; _t_, teeth. =B=, Interior of dorsal valve: _a.a_, anterior adductor (occlusor) scars; _a.p_, posterior adductor (occlusor) scars; _c.p_, cardinal process; _cr_, crura; _d.s_, dental sockets; _hp_, hinge-plate; _l_, brachial loop; _ss_, septum. (After Davidson.)]

In the Carboniferous genus _Syringothyris_ two special plates, situated between the dental plates, are rolled into an incomplete tube, so as to enclose probably the anal extremity of the alimentary canal; and in several genera a sub-umbonal “cardinal plate” is present, which is perforated (_Athyris_) or slit in some cases for the passage of the anal tube.

For the support of the fleshy “spiral arms” the calcareous structures forming the “brachial apparatus” are of two main types--(1) the loop type; (2) the spiral-cone type. In the _Strophomenidae_ no special calcareous support seems to have been usually present (Fig. 334), though in some species of _Leptaena_ spirally-grooved elevated areas supported the fleshy arms; in the _Productidae_ it is probable that the ridges enclosing the “reniform impressions” (Fig. 333, _i_) served for a similar purpose.

The _Terebratulidae_ show the “loop type” of brachial apparatus. In _Waldheimia_ (Fig. 329), which may be taken as an example, we notice first in the dorsal valve the “crura” (_cr_), from which arise the two “descending branches” which run forwards and then are bent back to form the “ascending branches” which are united by the “transverse band.” In some genera the “ascending branches” may be reduced to mere points, and the “transverse band” become a median vertical plate; the “crura,” too, may be fused so as to form a “crural band”; and the “descending branches” may be connected by a cross band--the “jugal band.” In _Stringocephalus_ (Fig. 326, _l_, _s.p_) the loop is furnished on its inner edge with radiating processes; and in _Argiope_ the loop is simple, not reflected, and fused with marginal septa; while in the _Thecidiidae_ it is more or less fused with the shell itself, and with the mass of calcareous spicules secreted by the mantle.

The “spiral-cone type” of brachial apparatus is found in the _Spiriferidae_, _Atrypidae_, and _Koninckinidae_, and consists of two spirally-enrolled calcified lamellae, forming two cones with their apices directed laterally (_Spirifera_, Fig. 330), or towards the interior of the dorsal valve (_Atrypa_, Fig. 332), or towards each other (_Glassia_); or forming two flat spirals in the same plane (_Koninckinidae_). A “jugal band” is generally present, but varies much in position, and in some genera has complicated posterior processes.

The _Rhynchonellidae_ have no loop or spiral cones, but merely a pair of short “crura.”

[Illustration: FIG. 330.--_Spirifera striata._ (Carboniferous Limestone.) Showing brachial spires.]

The principal modifications in the attachments of the muscles in the _Testicardines_ are illustrated by _Productus giganteus_ (Fig. 333), _Leptaena rhomboidalis_ (Fig. 334), and _Waldheimia flavescens_ (Fig. 329).

In _Productus_ (Fig. 333) we see in the ventral valve a pair of dendritic occlusor, often called adductor, impressions and a pair of large flabellate divaricator impressions. In the dorsal valve the large “cardinal process” served for the attachment of the divaricator, and a low median septum separated the dendritic occlusor scars, which are rarely divisible into anterior and posterior pairs.

[Illustration: FIG. 331.--_Atrypa reticularis._ (Wenlock Limestone.)]

[Illustration: FIG. 332.--Interior of the same, seen from the dorsal side, showing brachial spires. (After Hall.)]

In _Leptaena_ (Fig. 334) the occlusor scars (_a_) in the ventral valve are narrow and median, and are enclosed by a pair of flabelliform divaricator impressions (_d.v_); in the dorsal valve two pairs of occlusor scars (_a.a_, _p.a_) are well marked, and accessory posterior occlusor scars are traceable in some specimens. The vascular sinuses (_v.s_) and genital areas are conspicuous in many species of this and other genera.

[Illustration: FIG. 333.--_Productus giganteus._ (After Woodward.) Carboniferous Limestone. =A=, Interior of dorsal valve. =B=, Interior of ventral valve. =C=, Transverse section of valves. =D=, Hinge line of =A=: _a_, occlusor scars; _d_, divaricator scars; _i_, “reniform impressions”; _ca_, cardinal process; _h_, hinge line; _p_, brachial prominence; _s_, cavity for spiral arms; _do_, dorsal valve; _ve_, ventral valve.]

In _Waldheimia_ (Fig. 329) a sub-umbonal “peduncular muscle” scar (_p_) in the ventral valve has before it a pair of “accessory divaricator” scars (_a.d_) flanked by a pair of “ventral adjustor” (_v.a_) and a pair of “divaricator” impressions (_d_), between which lie the two occlusor scars (_a_). In the dorsal valve anterior and posterior pairs of occlusor scars (_a.a_, _a.p_) are visible.

The minute structure of the calcareous shell of the Testicardines is of flattened fibrous prisms inclined at a very acute angle to the surfaces. In many forms minute tubes more or less closely arranged pierce through the fibrous shell-substance; but in some genera (_Productus_) they do not reach the outer surface (see p. 468). Allied genera, however, differ much in the punctate or impunctate character of the shell.

[Illustration: FIG. 334.--_Leptaena rhomboidalis._ (Silurian.) =A=, External view of ventral valve. =B=, Interior of ventral valve: _a_, occlusor scars; _d_, pseudo-deltidium; _d.v_, divaricator scars; _c.a_, hinge area; _t_, teeth. =C=, Interior of dorsal valve: _a.a_, anterior occlusor scars; _p.a_, posterior occlusor scars; _c.a_, hinge area; _c.p_, cardinal process; _d_, chilidium; _s_, dental sockets; _v.s_, vascular sinuses.]

SYNOPSIS OF FAMILIES

I. ECARDINES

Family. _Lingulidae_

Shell elongated, composed of alternating chitinous and calcareous layers, the latter of which are perforated. Attached by a pedicle passing between apices of valves.

Arms have no calcified supports.

(For muscles see Fig. 322.)

RANGE.--Lower Cambrian to Recent.

PRINCIPAL GENERA.--_Lingula_, _Lingulella_, _Lingulepis_.

Family. _Obolidae_

Shell varies in shape. Ventral valve provided with pedicular groove or foramen. Cardinal border thickened. No brachial supports. Shell composed of alternating chitinous and calcareous layers.

(For muscles see p. 496.)

RANGE.--Lower Cambrian to Devonian.

PRINCIPAL GENERA.--_Obolus_, _Obolella_, _Kutorgina_, _Linnarssonia_, _Siphonotreta_, _Acrotreta_, _Neobolus_.

Family. _Discinidae_

Shell rounded, valves more or less conical, fixed by pedicle passing through slit or tubular foramen in ventral valve. No calcified brachial supports. Shell structure chitino-calcareous.

RANGE.--Ordovician to Recent.

PRINCIPAL GENERA.--_Discina_, _Orbiculoidea_, _Trematis_.

Family. _Craniidae_

Shell calcareous, subcircular; fixed by surface of ventral valve; dorsal valve the larger, depressed-conical. Shell structure punctate.

Four principal muscular scars in each valve, with central triangular protuberance in ventral valve (see p. 476).

RANGE.--Ordovician to Recent.

PRINCIPAL GENUS.--_Crania_.

Family. _Trimerellidae_

Shell thick, calcareous, inequivalve; beak of ventral valve usually prominent; rudimentary teeth maybe present; hinge area well developed, with pseudo-deltidium. In interior of valves muscular platform, “crescent,” and sometimes sub-umbonal chambers (see p. 494, Fig. 323).

RANGE.--Ordovician and Silurian; maximum in Wenlock.

PRINCIPAL GENERA.--_Trimerella_, _Monomerella_, _Dinobolus_, _Rhinobolus_.

II. TESTICARDINES

Family. _Productidae_

Shell entirely free, or fixed by ventral valve or spines. Concavo-convex, more or less covered with tubular spines. Hinge line straight. Hinge-teeth absent or rudimentary.

Cardinal process prominent.

Reniform impressions in dorsal valve.

(For muscular impressions see p. 501, Fig. 333.)

RANGE.--Silurian to Permian. Genus _Productus_ very characteristic of the Carboniferous.

PRINCIPAL GENERA.--_Productus_, _Chonetes_, _Strophalosia_, _Proboscidella_, _Aulosteges_.

Family. _Strophomenidae_

Shell very variable in shape; concavo-convex, plano-convex, or biconvex; hinge line usually straight; frequently with an area on each valve; foramen may or may not be present. Shell structure near always punctate. Ventral valve usually furnished with hinge-teeth; and dorsal valve with cardinal process.

Brachial supports completely absent or very rudimentary.

(For muscular impressions see p. 502, Fig. 334.)

RANGE.--Wholly Palaeozoic.

PRINCIPAL GENERA.--_Orthis_, with many sub-genera, _Clitambonites_, _Skenidium_, _Strophomena_, _Orthothetes_, _Leptaena_, _Stropheodonta_, _Plectambonites_.

Family. _Koninckinidae_

Shell plano-convex or concavo-convex. Brachial apparatus composed of two lamellae spirally enrolled in the same plane, or in the form of depressed cones, with the apices directed into the ventral valve.

RANGE.--Silurian to Lias.

PRINCIPAL GENERA.--_Koninckina_, _Koninckella_, _Coelospira_, _Davidsonia_.

Family. _Spiriferidae_

Shell biconvex. Brachial apparatus consisting essentially of two descending calcareous lamellae which by spiral enrolment form a pair of laterally-directed cones (Fig. 330).

RANGE.--Chiefly Palaeozoic, but a few forms pass up into the Lias.

PRINCIPAL GENERA.--_Spirifera_, _Cyrtia_, _Uncites_, _Athyris_, _Merista_.

Family. _Atrypidae_

Brachial apparatus consists of two descending calcareous lamellae which bend outwards at the extremity of the crura and are coiled into two spiral cones, the apices of which either converge towards each other (_Glassia_) or towards the dorsal valve (_Atrypa_, Fig. 332), or diverge towards the dorsal valve (_Dayia_); shell structure impunctate.

RANGE.--Ordovician to Trias.

PRINCIPAL GENERA.--_Atrypa_, _Dayia_, _Glassia_.

Family. _Rhynchonellidae_

Shell biconvex, hinge line usually curved.

Beak of ventral valve incurved, with foramen.

Calcareous brachial supports reduced to a pair of short curved crura.

The septa, dental and socket plates may be highly developed and divide up the cavity of the shell into chambers (_Stenochisma_, _Conchidium_).

Shell structure fibrous, rarely punctate; muscular impressions as in _Terebratulidae_.

RANGE.--Ordovician to Recent: majority of the genera are Palaeozoic.

PRINCIPAL GENERA.--_Rhynchonella_ (Fig. 327), _Stenochisma_, _Stricklandia_, _Conchidium_.

Family. _Terebratulidae_

Shell structure punctate.

Arms supported by a calcareous loop, usually bent back on itself.

(For muscular impressions see p. 502, Figs. 328, 329.)

Beak of ventral valve perforated by foramen, furnished with deltidium.

RANGE.--Devonian to Recent; maximum development in Mesozoic times.

PRINCIPAL GENERA.--_Terebratula_, _Terebratulina_, _Waldheimia_, _Terebratella_, _Kingena_, _Magas_, _Centronella_.

Family. _Argiopidae_

Large foramen for passage of pedicle. Marginal septa present in both valves. Calcareous brachial loop follows margin of shell and is more or less fused with the septa. Shell structure punctate.

RANGE.--Jurassic to Recent.

PRINCIPAL GENERA.--_Argiope_, _Cistella_.

Family. _Stringocephalidae_

Shell subcircular, punctate. Cardinal process highly developed, bifid. Brachial apparatus composed of two calcareous free lamellae, prolonged at first downwards, then bent back, upwards and outwards to run parallel to margin of shell and to unite in front, thus constituting a wide loop.

RANGE.--Silurian and Devonian.

SOLE GENUS.--_Stringocephalus_.

Family. _Thecidiidae_

Shell usually fixed by beak of ventral valve, plano-convex. Sub-cardinal apophysis in ventral valve for attachment of occlusors. Marginal septa in dorsal valve. Calcareous brachial loop more or less fused with shell, and with calcareous spicules of mantle. Shell structure: inner layer fibrous, outer layer tubulated.

RANGE.--Carboniferous to Recent.

PRINCIPAL GENERA.--_Thecidium_, _Oldhamina_.

STRATIGRAPHICAL DISTRIBUTION OF BRACHIOPODA

It is remarkable that some of the earliest types of Brachiopoda exist generically unchanged at the present day. Such are _Lingula_, ranging from the Cambrian; _Discina_ and _Crania_, ranging from the Ordovician; and amongst the hinged forms _Terebratula_ from the Devonian, and _Rhynchonella_ from the Ordovician.

In the lowest Cambrian (Olenellus beds) the most important genera are _Linnarssonia_ and _Kutorgina_. The hinged forms appear in the Cambrian, being represented by _Orthis_; but the majority in this formation belong to the Ecardines. _Lingula_, _Lingulella_, and _Obolella_ are characteristic.

In the Ordovician many new genera of the Testicardines make their appearance, such as _Strophomena_, _Leptaena_, _Atrypa_, _Rhynchonella_, _Clitambonites_, etc., but the extraordinary abundance and variety of _Orthis_ is most remarkable. The Ecardines are reinforced by such forms as _Trematis_ and _Siphonotreta_. It is, however, in the Silurian that the Testicardinate Brachiopoda attain their maximum, for in addition to a great development of species amongst the older forms, a host of new genera for the first time occur here (_Spirifera_, _Athyris_, _Conchidium_, _Stricklandia_, _Chonetes_, _Cyrtia_, etc.); and the _Trimerellidae_ are especially characteristic of the Wenlock.

With the commencement of Devonian times many species and genera become extinct, but new forms come in (_Terebratula_, _Orthothetes_, _Productus_, etc.), and some genera are wholly confined to this formation (_Uncites_, _Stringocephalus_). The Carboniferous is marked by the maximum development of _Productus_ and _Spirifera_; _Orthothetes_, _Stenochisma_, and _Athyris_ are also abundant, but there is a considerable extinction of the older genera and species, and a great diminution in the number of individuals and species of those that persist.

A further reduction occurs in the Permian, where the most important genera are _Productus_, _Strophalosia_, and _Stenochisma_; but _Aulosteges_ is a new form peculiar to this period. In the Trias a new era commences; the principal families and genera of the older rocks disappear entirely; a few spire-bearing genera persist (_Spiriferina_, _Athyris_), and the genus _Koninckina_ is restricted to this formation.

The enormous development of species of the _Terebratulidae_ and _Rhynchonellidae_ is the most noticeable feature in Jurassic times; and a few ancient types linger on into the Lias (_Spiriferina_, _Suessia_, a sub-genus of _Spirifera_); _Koninckella_ here occurs.

The Cretaceous Brachiopoda are closely allied to the Jurassic; _Magas_ and _Lyra_ are peculiar to the period, and the _Terebratulidae_ and _Rhynchonellidae_ are very abundant, together with the Ecardinate genus _Crania_.

With the commencement of Tertiary times the Brachiopoda have lost their geological importance, and have dwindled down into an insignificant proportion of the whole Invertebrate fauna.

* * * * *

The distribution of the Brachiopoda in past time is shown in the following table:--

+------------------------------------+-----------------------+-----------+-------+ | | Palaeozoic | Mesozoic | | | | | | | | C | | | | | | | | | | | | | a | | | | | | | | | | | | | r | | | | | | | | | | O | | | b | | | | C | | | | | | r | | | o | | | | r | | | | | C | d | S | D | n | | | J | e | T | | | | a | o | i | e | i | P | | u | t | e | | | | m | v | l | v | f | e | | r | a | r | R | | | b | i | u | o | e | r | T | a | c | t | e | | | r | c | r | n | r | m | r | s | e | i | c | | | i | i | i | i | o | i | i | s | o | a | e | | | a | a | a | a | u | a | a | i | u | r | n | | | n | n | n | n | s | n | s | c | s | y | t | | ECARDINES +---+---+---+---+---+---+---+---+---+---+---+ | Lingulidae Lingula |___|___|___|___|___|___|___|___|___|___|___| | Lingulella |___| | | | | | | | | | | | Obolidae Obolus | |___|___| | | | | | | | | | Obolella |___|___| | | | | | | | | | | Kutorgina |___|___| | | | | | | | | | | Linnarssonia |___| | | | | | | | | | | | Trematis | |___|___| | | | | | | | | | Siphonotreta | |___|___| | | | | | | | | | Acrotreta | |___| | | | | | | | | | | Discinidae Discina | |___|___|___|___|___|___|___|___|___|___| | Craniidae Crania | |___|___|___|___|___|___|___|___|___|___| | Trimerellidae Trimerella | | |___| | | | | | | | | | Dinobolus | |___| | | | | | | | | | | | | | | | | | | | | | | | TESTICARDINES | | | | | | | | | | | | | Productidae Productus | | | |___|___|___| | | | | | | Chonetes | | |___|___|___| | | | | | | | Strophalosia | | | |___|___|___| | | | | | | Strophomenidae Orthis |___|___|___|___|___| | | | | | | | Skenidium | |___|___| | | | | | | | | | Clitambonites | |___| | | | | | | | | | | Strophomena | |___|___| | | | | | | | | | Stropheodonta | |___|___|___| | | | | | | | | Leptaena | |___|___|___|___| | | | | | | | Orthothetes | | | |___|___|___| | | | | | | Davidsonia | | | |___| | | | | | | | | Koninckinidae Koninckina | | | | | | |___| | | | | | Koninckella | | | | | | | |___| | | | | Spiriferidae Spirifera | | |___|___|___|___| | | | | | | Spiriferina | | | |___|___|___|___|___| | | | | Cyrtia | | |___|___|___| | | | | | | | Syringothyris | | | | |___| | | | | | | | Uncites | | | |___| | | | | | | | | Athyris | | |___|___|___|___|___| | | | | | Merista | | |___|___| | | | | | | | | Retzia | | |___|___|___|___|___| | | | | | Atrypidae Atrypa | |___|___|___|___|___|___| | | | | | Dayia | | |___| | | | | | | | | | Coelospira | | |___| | | | | | | | | | Rhynchonellidae Rhynchonella | |___|___|___|___|___|___|___|___|___|___| | Stenochisma | | | |___|___|___| | | | | | | Stricklandia | | |___| | | | | | | | | | Conchidium | | |___|___| | | | | | | | | Terebratulidae Terebratula | | | |___|___|___|___|___|___|___|___| | Terebratulina | | | | | | | |___|___|___|___| | Waldheimia | | | | | | | |___|___|___|___| | Terebratella | | | | | | | |___|___|___|___| | Kingena | | | | | | | |___|___| | | | Magas | | | | | | | | |___| | | | Centronella | | |___|___|___| | | | | | | | Argiopidae Argiope | | | | | | | |___|___|___|___| | Cistella | | | | | | | |___|___|___|___| | Stringocephalidae Stringocephalus | | | |___| | | | | | | | | Thecidiidae Thecidium | | | | | | |___|___|___|___|___| | Oldhamina | | | | |___| | | | | | | | | | | | | | | | | | | | +------------------------------------+---+---+---+---+---+---+---+---+---+---+---+

PHYLOGENY AND ONTOGENY

Wherever successive stages in the life history of an individual resemble in important anatomical features the adult individuals of other species occurring in successive members of a stratigraphical series, the development of the individual may be regarded as an epitome of the development of the species; it also generally throws light on the origin and relationships of allied genera and families.

In the case of the fossil Brachiopoda comparatively little work has yet been done in tracing their ontogeny or phylogeny, though the abundance, variety, and excellent state of preservation of the extinct species offer a promising field for investigation. It is to Dr. C. E. Beecher and other recent American palaeontologists that we owe our advance in this branch of the subject.

In the first place, in about forty genera, representing nearly all the leading families of the group, the important fact has been established of the presence of a common form of embryonic shell, termed the “protegulum,” which is “semicircular or semielliptical in shape with a straight or arcuate hinge line and no hinge area” (Beecher).[431] Its minute size and delicate texture cause its preservation to be rare, but its impression is not uncommonly left on the beak of the adult shell.

The main features of this embryonic shell are exhibited in the adult Lower Cambrian Brachiopod _Obolus_ (_Kutorgina_) _labradoricus_ (Billings); the sub-equal semielliptical valves have lines of growth running concentrically and parallel to the margin of the shell, and ending abruptly against the straight hinge line; and this indicates that there has been no change in the outline and proportions of the shell during its stages of growth, but only a general increase in size. It is very significant that we have here a mature type possessing the common embryonic characters of a host of widely separated genera, and we may therefore regard it as the most primitive form known.

Many genera pass through this so-called “Paterina” stage either in the case of both their valves, or more generally in the case of the dorsal valve only; but modifications in the form of the protegulum arise, which are due to the influence of accelerated growth, by which features belonging to later stages become impressed on the early embryonic shell. The most variable and specialised valve--the ventral or pedicle valve naturally exhibits the effect of this influence first and to the greatest extent. The Palaeozoic adult forms of many species represent various pre-adult stages of the Mesozoic, Tertiary, and Recent species, as is especially well shown in the genera _Orbiculoidea_ and _Discinisca_.

In the Strophomenoid shells the protegulum in the dorsal valve is usually normal, but in the ventral valve abbreviation of the hinge and curvature of the hinge line are produced by acceleration of the “Discinoid stage” in which a pedicle notch is present.

No marked variation has yet been noticed in the spire-bearing, or Terebratuloid, or Rhynchonelloid genera.

The form of the shell and the amount of difference in shape and size of the valves seem to be largely due to the length of the pedicle and its inclination to the axis of the body, as evidenced by the development of _Terebratulina_. A series showing progressive dissimilarity of the two valves arising from these causes can be traced from _Lingula_ to _Crania_. The greater alteration that takes place in the ventral valve appears to be due to its position as lower and attached valve. If the pedicle is short a transversely-expanded shell with long hinge line results when the plane of the valves is vertical or ascending, but when the latter is horizontal a Discinoid form is found. This mode of attachment is often accompanied by a more or less plainly developed radial symmetry. Shells with long pedicles, on the other hand, are usually longer than wide.

The character of the pedicle-opening is of great significance from an evolutional and classificatory point of view, for the successive stages through which it passes in embryonic growth are chronologically paralleled by different genera, and are likewise accompanied by the successive acquisition of other important anatomical characters, as has been shown by Beecher and others. The first and simplest type of pedicle opening is in shells with a posterior gaping of the valves, where the pedicle protrudes freely between them in a line with the axis, and the opening is shared by both valves, though generally to a greater extent by the ventral valve. _Paterina_ (_= Obolus labradoricus_) and _Lingula_ furnish examples of this type. In the second type the pedicle opening is restricted to the ventral valve, and the direction of the pedicle makes a right angle with the plane of the valves; in the lower forms the pedicle lies in a slit or sinus (_Trematidae_), but by further specialisation it becomes enclosed by shell growth so as to lie within the periphery, and finally becomes sub-central in some genera (_Discinidae_). The third type shows the pedicle opening confined to the ventral valve and sub-marginal. A pseudo-deltidium may preserve the original opening (_Clitambonites_); or this shelly plate may become worn away or reabsorbed in the adult so that the deltidial fissure through which the pedicle passes remains quite open (_Orthidae_). In the fourth type the incipient stage marks a return to the simple conditions of the first type; but ultimately a pair of deltidial plates develop, and may completely limit the pedicle opening below. Examples of this type are _Spirifera_ and _Rhynchonella_. By means of these four types the Brachiopods have been divided into four Orders: the _Atremata_ (type i.); the _Neotremata_ (type ii.); the _Protremata_ (type iii.); and the _Telotremata_ (type iv.).

The _Telotremata_ were the last to appear, but the four types of pedicle-opening with the various forms of calcareous brachial apparatus were in existence in the Bala period of the Ordovician.

As _Paterina_ is the most primitive form of all, we may place it at the root of the phylogenetic tree. From it sprang the _Atremata_, which gave off the _Neotremata_ and _Protremata_; the most primitive _Neotremata_ seem to be the _Trematidae_, while the connecting link between the _Protremata_ and _Atremata_ is furnished by the _Kutorginidae_. From the genus _Conchidium_ and its allies we may see how the _Rhynchonellidae_ ushered in the _Telotremata_ as an offshoot from the _Protremata_. The _Telotremata_ subsequently gave off two main branches, which became specialised with the loop-bearing and spire-bearing forms respectively.

The evolution and mutual relationships of genera have been indicated with much probability by Hall, Clarke, and others. The Obolelloid type may be connected with the Linguloid by means of _Lingulella_ and _Linyulepis_, while in _Lingula_ itself we find the point of divergence for the ancestors of _Trimerella_, and for a line of variation culminating in _Dignomia_. The Palaeozoic Rhynchonelloids branched off at an early period from the same stock as _Orthis_, and are connecting links between this genus and Mesozoic Rhynchonellae; and a whole series of genera exhibit intermediate stages of structure between the Rhynchonelloid and Pentameroid groups. The Terebratuloids can be traced back to the primitive type _Renssoellaria_; and amongst spire-bearing forms, the protean genus _Spirifera_ can be split up into groups of species which diverge along lines tending to forms no longer congeneric. When we come to deal with specific differences we find frequently such a host of intermediate varieties that the separation of many species, as in the case of Mesozoic Terebratulae, is to a large extent arbitrary and artificial.

INDEX

References to figures are printed in thick type (=248=, =197=); to systematic position, in italics (_391_, _430_)

_Abralia_, _391_

Absorption of internal portions of shell, 259

Abyssal Mollusca, 374

_Acanthinula_, _441_

_Acanthoceras_, _399_

_Acanthochiton_, =403=, _403_

_Acanthodoris_, _434_

_Acanthopleura_, _403_; eyes, =188=

_Acavus_, 303, =304=, 335, _441_

_Acera_, 245, _430_

_Achatina_, 278, 328–337, =333=, _442_, =443=; jaw, =211=; food, 33; size of egg, 124; _A. fulica_, 279

_Achatinella_, 278, =326=, 327, _443_; radula, =234=; musical sounds, 51

_Achatinelloides_, 332

_Acicula_, 287, 296, _414_

_Acmaea_, _405_; radula, 227

_Acme_, _414_

_Acmella_, 314, _415_

_Acroptychia_, 336, _414_

_Acrotreta_, _504_, 508

_Actaeon_, 250, 427, =428=, _429_; radula, 217, 230; streptoneurous, 203 n.

_Actaeonella_, _430_

_Actaeonia_, _432_

_Actaeonina_, 250, _429_

_Actinoceras_, _394_

_Actinodonta_, _447_

_Acusta_, 306, 316, 318, _441_

_Adacna_, =12=, 297, _455_

_Adalaria_, _434_

_Adamsiella_, _414_

_Addisonia_, _412_

_Adelphoceras_, _395_

_Adeorbis_, _416_

_Admete_, _426_

_Aegires_, _434_

_Aegista_, 305, 316, _441_

_Aegoceras_, _398_

_Aeolis_, =10=, =152=, _432_; radula, 217, =229=; stinging cells, 65; mimicked by _Sagartia_, 68; warning coloration, 72

_Aerope_, 328, 333, _440_; radula, 215; habits, 54

Aestivation, 25

_Aetheria_, 328–336, _452_; variation, 92

_Africarion_, 333, _440_

_Agaronia_, _426_

Age of snails, 39

Aglossa, 7

Agnatha, habits, 51

_Akiodoris_, _434_

_Alaba_, _415_

_Alaria_, _418_

_Alariopsis_, _420_

_Albersia_, 320

Albino varieties, 87

_Alcadia_, 348–351, _410_

_Alderia_, _432_

_Alexia_, _439_

_Alicia_, _459_

_Allognathus_, _441_

_Allopagus_, _452_

Alloposidae, _384_

_Alvania_, _415_

_Alycaeus_, 266, 302 f., 309, 319, _414_

_Amalia_, _440_

_Amalthea_, 78

_Amaltheus_, _398_

_Amastra_, _443_

_Amaura_, _411_

_Amberleya_, _409_

_Ambonychia_, _449_

_Amicula_, _404_

_Ammonites_, 247, =393=, =398=, _398_; sutures, =396=; aptychus, =397=

Ammonoidea, _396_ f.

_Amnicola_, 325, _415_

_Amoria_, radula, 222

_Ampelita_, 335, _442_

_Amphibola_, 10, =18=, _439_; breathing, 151; radula, 236

_Amphibulimus_, 352, _442_; radula, 233

_Amphidoxa_, 358

_Amphidromus_, 301, 305, 317, =310=, 359, _442_; radula, 233

Amphineura, 8, _400_; breathing organs, 154, 168; nervous system, =203=; genitalia, 145

_Amphipeplea_, _439_

_Amphiperas_, _419_

_Amphisphyra_, _430_

_Amphissa_, _423_

_Amphitretus_, =383=

_Ampullaria_, 17, _416_; self-burial, 42; spawn, =125=; breathing organs, 151, =158=; jaws, =212=; shell, =249=, 263; operculum, =268=; distribution, 294, 320, 322, 343, 359

_Ampullarina_, 302, _439_

_Ampullina_, _411_

_Amussium_, _450_

_Amycla_, _423_

_Anabathron_, _415_

_Anachis_, _423_

_Anadenus_, 24, _441_

Anal glands, 241

Anal siphon, 164, 173

_Anastomopsis_, _442_

_Anatina_, 274, 275, _459_

Anatinacea, _458_; gills, 167

_Anaulus_, _414_

_Anchistoma_, 293, 296

_Ancilla_, 267, _426_

_Ancillina_, _426_

_Ancistrochirus_, _391_

_Ancistromesus_, _405_

_Ancistroteuthis_, _391_

_Ancula_, _434_; radula, 229, 230; warning coloration, 72

_Anculotus_, _417_

_Ancyloceras_, 247, _399_

_Ancylus_, 19, _439_; breathing, 162; hibernating, 27; radula, =235=

_Aneitea_, 325, _443_

_Angitrema_, 340, _417_

_Anisocardia_, _451_

_Anodonta_, 259, 341, _452_; shower of, 47; variation, 92; _Glochidium_, =147=; gill, =167=; otocyst, =197=; nervous system, =206=; hinge, 274; _A. anatina_, 24; distribution, 282

_Anodontopsis_, _451_

_Anoglypta_, 325, _441_

_Anomia_, =257=, _448_, 464; intestine, 241; byssus hole, =262=; hearing, 196

Anomiacea, _448_

_Anoplophora_, _451_

_Anostoma_, =248=, 266, 356, 358, _442_; aperture, =63=

_Anthracosia_, _451_

_Anura_, _424_

Anus, 209, 241

_Apera_, 334, _440_

_Aperostoma_, 344, _414_

_Aphanotrochus_, _408_

_Aphelodoris_, radula, 230

_Apicalia_, _422_

Aplacophora, 9, _404_; radula, 228

_Aplecta_, 354, _439_

_Aplustrum_, =245=, =428=, _430_; radula, 230

_Aplysia_, 245, =428=, _431_; stomach, 239; purple fluid, 65

_Aplysioidea_, _430_

_Aporrhais_, _418_; radula, 215

_Apricardia_, _455_

Aptychus, =397=

_Aptyxiella_, _417_

_Aptyxis_, _424_

Aral Sea, _Limnaea_ from near, =84=; _Cardium_ from, 91

_Arca_, =14=, 171, =273=, _448_; eyes, =191=

Arcacea, _448_

Arcachon, oyster-parks at, 105

_Arcestes_, _397_

_Archidoris_, =434=, _434_; protective coloration, 73

_Architeuthis_, 378, =390=, _390_; sucker, =381=

_Arcomya_, _458_

_Arconaia_, 307, _452_

Arctic shells, colour of, 86

_Arcuella_, _422_

_Argiope_, =470=, 472, 479, _487_; parasite of, 485; distribution, 486; fossil, 501, _506_, 508

Argiopidae, _506_, 508

_Argobuccinum_, _420_

_Argonauta_, =383=, _383_; egg-laying, 127; hectocotylised arm, 137; radula, 236

_Arinia_, _413_

_Ariolimax_, _441_, 341; radula, 233

_Arion_, _440_; shell, 175, 245, 246; hardier than _Helix_, 24; voracity, 30 f.; egg-laying, 42 f.; protective coloration, 70; pulmonary orifice, 160; food, 179; smell, 193 f.; radula, 233; distribution, 285

_Arionta_, =341=, 353, _441_

_Ariophanta_, 301, =308=, 309, 316, _440_; protective coloration, 70

Aristotle, on modified arm of polypus, 138

_Artemis_, _454_

_Arthuria_, _403_

_Asaphis_, _456_

_Ascoceras_, _394_

Ascoglossa, 11 n., _431_

Ashford, C., on pulsations of heart in _Helix_, 26; on homing of _Helix_, 35; on dart-sac, 143

_Asolene_, _416_

_Aspergillum_, 262, _459_

_Aspidelus_, 329, _440_

_Aspidoceras_, _399_

_Assiminea_, _415_

_Astarte_, _451_

_Asthenothaerus_, _459_

_Astralium_, _409_

_Athoracophorus_, _443_--see _Janella_

_Athyris_, 499, 500, _505_; stratigraphical distribution, 507, 508

_Atilia_, _423_

_Atlanta_, 421, _422_; foot, 200

_Atopocochlis_, 330, _441_

Atremata, 511

_Atretia_, distribution, 486, _487_

_Atrypa_, 501, =502=, _505_; stratigraphical distribution, 507, 508

Atrypidae, 501, 505, 508

_Aturia_, 393, _395_

_Atys_, =428=, _430_

Aucapitaine, H., on tenacity of life, 38

_Aucella_, _449_

_Aulopoma_, 157, 304, _414_; operculum, =269=

_Aulosteges_, _504_; stratigraphical distribution, 507

_Auricula_, =439=, _439_

_Auriculella_, 327, _443_

Auriculidae, 17, =18=, =260=, =439=, _439_; lung, 160; eyes, 186; radula, 235

_Austenia_, 301, 304, _440_

_Avellana_, _430_

_Avicula_, 254, 258, =449=, _449_; eyes, 190; genital orifice, 242; _A. margaritifera_, 100

_Aviculopecten_, _450_

_Aviculopinna_, _449_

_Axinus_, _452_

_Azeca_, _442_

Azygobranchiata, 155, 407

_Babinka_, _447_

_Bactrites_, _395_

_Baculites_, _399_

_Baikalia_, 290, _415_

Baird, Mr., on the British Museum snail, 37

_Balea_, _442_; _B. perversa_, 24, 41

Baltic, fauna of the, 12, 83, 366

_Bankivia_, _408_

_Barbatia_, _448_

_Barleeia_, _415_

Barnacle, Rev. H. G., on musical sounds, produced by Mollusca, 51

Barometers, snails as, 50

_Bartlettia_, _452_

_Basilissa_, 376, _408_

Basommatophora, 11, 19, 181, _438_

_Basterotia_, _451_

Bateson, W., on variation in _Cardium_, 91; on hearing in _Anomia_, 196

_Bathmoceras_, _395_

_Bathydoris_, _433_

_Bathyteuthis_, _390_

_Batissa_, 320, _453_

_Beddomea_, 304

Beecher on phylogeny, 509

Beetles, prey on Mollusca, 58

_Bela_, _426_; radula, =219=

_Belemnites_, 380

Belemnitidae, _387_

_Belemnosepia_, _390_

_Bellerophon_, =266=, _407_

_Belopetra_, 380

Belopteridae, _388_

_Belosepia_, 386, _388_

_Beloteuthis_, _390_

_Bembix_, 376, _408_

_Benedictia_, 290, _415_

_Benthobia_, 377

_Benthodolium_, 377

_Berendtia_, _441_

Beudant, experiments on Mollusca, 12

Bideford Bridge and mussels, 117

Binney, Dr., on epiphragm, 28

_Binneya_, 341, _441_

_Biradiolites_, _456_

Birds, devour Mollusca, 56 f.

_Bithynella_, 289, 293, _415_

_Bithynia_, 336, 342, _415_; stomach, 239; habitat, 25

_Bittium_, _416_

_Blaesospira_, 346, 351

_Blandiella_, 16, _414_

_Blanfordia_, _414_

Blind Mollusca, 185

Blood, 171

Bodö, land Mollusca, 24

Boeuf and French oysters, 107

_Bolma_, _409_

_Boltenia_, _346_

_Boreofusus_, radula, 221

_Bornella_, _433_; stomach, 239

_Borsonia_, _426_

_Borus_, 356–358, _441_

_Bourcieria_, 357, _410_

_Bourguetia_, _417_

_Bourguignatia_, 332

Bouvier--_see_ Fischer

_Boysia_, 302, _442_

Brachial apparatus, types of, 500

Brachiopoda, fossil, limestone formed of, 492; shell, 493, 497; muscle scars on, 494, 501; platform, 495; synopsis of families, 503; stratigraphical distribution, 506; phylogeny and ontogeny, 509; Orders, 511

Brachiopoda, recent, 463; historical account of, 464; shell, 465; body, 469; digestive system, 471; body cavity, 472; heart, 473; excretory organs, 474; muscles, 475; nervous system, 478; reproductive system, 478; embryology, 479; habits, 482; distribution, 484; classification, 487; affinities, 487

_Brachytrema_, _417_

Brackish-water species, 14

Branchiae, 151, 153, 164

Branchial siphon, 155, 164, 173

Braun, on self-impregnation, 44

Breathing organs--_see_ Respiration, Branchiae

_Brechites_, _459_

Breeding, periodicity in, 129

_Broderipia_, _408_

_Brotia_, 305

_Brownia_, 133

_Buccinanops_, _423_

_Buccinopsis_, _424_; radula, 221, 222; egg-laying, 128

_Buccinum_, =6=, _424_; radula, 217; monstrosity, =251=; breeding, 129; osphradium, =195=; spawn, =126=

_Buliminus_, 24, 278, 285, =295= f., 316, 331, 339, _442_; protective habits, 70; _B. pallidior_, 38

_Bulimulus_, 278, 334, 339–359, _442_; jaw, =211=, 233; radula, 233; variation, 87

_Bulimus_, 278, 342–359, =355=, _441_; radula, 233; egg, =124=

_Bulinus_--see _Isidora_

_Bulla_, 428, _430_

_Bullia_, =155=, _423_; habits, 192; foot, 198; radula, 221

Bulloidea, _429_

Burrowing Mollusca, 446

Burying propensities of Mollusca, 27, 41

_Busycon_, _424_; money made from, 97; egg-capsules, =125=--see _Fulgur_

Butterell, Mr., on habits of _Testacella_, 52

_Byssocardium_, _455_

Byssus gland, 201

_Cadlina_, _434_

_Cadoceras_, =393=

_Cadulus_, 376, _445_

_Caecilianella_, _442_; habitat, 48; eyes, 186

_Calcarella_, 133

California, land Mollusca, 280

_Calliostoma_, _408_; jaws, =212=

_Callistochiton_, _403_

_Callochiton_, _403_

_Callogaza_, _408_

_Callonia_, _442_

_Callopoma_, _409_

_Calma_, protective coloration, 74

_Calybium_, _410_

_Calycia_, 320, _442_

_Calycidoris_, _434_

_Calyptraea_, =248=, _412_

_Camaena_, 305, 306, 315, =316=, _441_

Cambrian, Mollusca of the, 2

_Camitia_, _409_

_Campaspe_, _433_

_Camptoceras_, =302=

_Camptonyx_, 278, =302=, _439_

_Campylaea_, 285, 289 f., =293=, _441_

Canal, 155

_Cancellaria_, _426_

_Canidia_, 16, 305, _423_

Cannibalism in snails and slugs, 32, 33

_Cantharidus_, _408_

_Cantharus_, 275; radula, =222=

_Caprina_, _456_

_Caprotina_, _456_

_Capulus_, _412_

_Caracolus_, =347=-351, _441_

_Carbonicola_, _451_

Cardiacea, _454_

_Cardiapoda_, _421_

_Cardilia_, _454_

Cardinal plate, 500

Cardinal process, 497, 501

_Cardinalia_, _408_

_Cardinia_, _451_

_Cardita_, =273=, _451_

_Carditella_, _451_

_Carditopsis_, _451_

_Cardium_, =6=, =273=, =455=, _455_; _C. edule_, =12=, =164=; modifications, 12; variation, 84, =91=; nervous system, 207; distribution, 292, 297

_Carelia_, 327, _443_

_Carinaria_, =9=, =422=, _422_; foot, 200

_Carinifex_, _439_

_Carolia_, _448_

_Cartusiana_, 296

_Carychium_, 18, _439_

_Caryodes_, 325, 359, _441_

_Casella_, radula, 230

_Caspia_, 12, 297

Caspian Sea, fauna, 12, 297

_Cassidaria_, _420_

_Cassidula_, =18=, 278, =439=, _439_

_Cassis_, 255, _420_; radula, =223=

_Castalia_, 344, _452_

_Cataulus_, 157, 266, 304, _414_

Caterpillars mimicking _Clausilia_, 68

_Cathaica_, 316, _441_

_Catinella_, _443_

_Cavolinia_, 158, _436_; eyes, 186

_Cecina_, _414_

_Cenia_, _432_; breathing, 152

_Centrodoris_, _434_; radula, 230

_Centronella_, 499, _506_, 508

Cephalopoda, 378 f.; defined, 5; ink, 65; egg-laying, 127; embryo, =133=; branchiae, 168; osphradium, 195; foot, 200; nervous system, 206; jaws, 213; radula, 236

_Cepolis_, 349–351, _441_

_Cerastoma_, _423_

_Cerastus_, 331, _441_

Cerata of Nudibranchs, 71, 159

_Ceratites_, _397_, =398=; suture, =396=

_Ceratodes_, 357, _416_

_Ceres_, =21=, 354, _410_

_Ceritella_, _417_

_Cerithidea_, 260, _417_; _C. obtusa_, breathing, 152

_Cerithiopsis_, _417_

_Cerithium_, =16=, _416_

_Ceromya_, _458_

_Chaetoderma_, =404=, _404_; breathing organs, =154=; nervous system, =203=; radula, 217, 228

_Chaetopleura_, _403_

_Chama_, 257, 272, 446, _455_

_Chamostrea_, _458_

Changes in environment, effect of, 83 f.

Chank-shell, fishery of, 100

_Charis_, 324, _442_

_Charopa_, 319, 323–327, _441_

_Chascax_, _424_

_Chelinodura_, _430_

_Chelotropis_, 133

_Chenopus_, _418_

Chilidium, 498

_Chilina_, 19, _343_, 358

Chilinidae, _439_; radula, 236

_Chilotrema_, _441_

China, use of shells in, 101

_Chiropteron_, 133

_Chiroteuthis_, 385, _391_

_Chiton_, =8=, =153=, _403_; egg-laying, 126; breathing organs, 153 f.; eyes, =188=; osphradium, 195; radula, =228=; nervous system, =203=; valves, =401=, =402=; girdle, =403=

_Chitonellus_, =404=, _404_; valves, =401=

_Chittya_, 16, 348, 351, _414_

_Chlamydephorus_, 333, _440_

_Chlamydoconcha_, 175, 245, _453_

_Chlamys_, _450_

_Chloritis_, 306, 311, 319–324, _441_

_Chlorostoma_, _408_

_Chlorostracia_, 307

_Choanomphalus_, 250, 290, _439_

Chondrophora, _389_

_Chondropoma_, 346–355, =348=, _414_

_Chondrula_, 285, =295=, 296, _442_

_Choneplax_, _404_

_Chonetes_, _504_; stratigraphical distribution, 507, 508

_Choristes_, _420_

_Choristoceras_, _398_

_Chorus_, _423_

_Chromodoris_, _434_; jaws, =212=; radula, 230

_Chrysallida_, _422_

_Chrysodomus_, _423_

_Chrysostoma_, _409_

_Cingula_, _415_

_Cingulina_, _422_

_Cionella_, _442_

_Circe_, _454_, =458=

Circulatory system, 169

_Circulus_, _408_

Circumpolar species, 287

_Cirrhoteuthis_, 381, =382=

_Cistella_, 467, =470=, 472, 475, 476, 479, 480, _487_; larvae, =481=, 483; parasite of, 485; distribution, 486; fossil, _506_, 508

_Cistopus_, _385_

_Cistula_, 349, 351, 355, _414_

Cladohepatica, _432_

_Clanculus_, _408_

Classification, 5, 8; of Gasteropoda, 8, 11

_Clathurella_, _426_

_Clausilia_, =442=, _442_; mimicked by caterpillars, 68; monstrosity, 251; distribution, 285 f., =294=, 305–318, 332, 339–356; _C. rugosa_, 24; _scalaris_, 278

_Clavagella_, 262, _459_

_Clavator_, 335, 359, _441_

_Clavatula_, _426_

_Clavella_, _424_

_Claviger_, 329, _417_

_Clea_, =16=, 305, _423_

_Clementia_, _454_

_Cleodora_, =436=, _436_

_Cleopatra_, 294, 328, 331, 336, _416_

Clessin, on duration of life, 39

_Clessinia_, 12, 297

_Clio_, =436=, _436_

_Cliona_, enemy of oysters, 112

_Clione_, 158, _438_

_Clionopsis_, _437_

_Clitambonites_, 498, _505_; stratigraphical distribution, 507, 508, 511

_Clithon_, 327, _410_

_Clydonites_, _398_

_Clymenia_, _397_

_Clypidella_, _406_

_Cocculina_, _408_

_Cochlicella acuta_, 278

_Cochliolepas_, 77

_Cochloceras_, _398_

_Cochlodésma_, _459_

_Cochlostyla_, 124, 278, =313=, 315, _441_

Cockles, use of, 101, 118

_Coecum_, 247, =260=, _417_, =418=

_Coeliaxis_, 334, _442_; habitat, 49

_Coelocentrum_, =353=, _442_

_Coelospira_, _505_, 508

Cold winter, effect on oysters, 112; on mussels, 116

Collinge, W. E., on growth and burial of shells, 41

_Collisella_, _405_

_Collisellina_, _405_; radula, 227

_Collonia_, _409_

_Colobocephalus_, _430_

Colour of arctic shells, 86

_Colpodaspis_, _430_

_Columbarium_, _426_

_Columbella_, _423_; radula, =222=

_Columbellaria_, _420_

_Columbellina_, _420_

_Columna_, 328, =330=, _443_

_Cominella_, =16=, _424_

Composition of shell, 252

_Concha_, 463

_Conchidium_, 497, =498=, 500, _505_; stratigraphical distribution, 507, 508, 511

_Concholepas_, 267, _423_

_Conidea_, _423_

_Conocardium_, _455_

_Conorbis_, _426_

_Conus_, 247, 275, _426_; poisonous bite, 65; tooth, =66=; shell, =69=, =255=, 260; mimicked by _Strombus_, 69; prices given for rare, 121; spawn, =125=; radula, 218, =220=; operculum, =269=

_Cookia_, _409_

_Coptochilus_, 314, _414_

_Coralliophaga_, _451_

_Coralliophila_, 75, _423_

Coralliophilidae, radula, 216

_Corambe_, _434_

_Corasia_, 311, 319–321

_Corbicula_, 15, 288, 292 f., _453_

_Corbis_, _452_

_Corbula_, _456_

_Corilla_, 303

_Corona_, 27, _442_

_Coronaria_, =297=

_Coryda_, 346–351, _441_

_Coryphella_, _432_

_Cosmoceras_, _399_

Cowry used as money, 96

Coyote trapped by _Haliotis_, 57

_Cranchia_, _391_

Crania, 464, =467=, 468, 469, 471, 472, 473, 475, 476, =477=, _487_; distribution, 485; fossil, 493, 494, _504_; stratigraphical distribution, 506, 507, 508, 510

Craniidae, _487_, 496, _504_, 508

_Cranopsis_, =265=, _406_

_Craspedochiton_, _403_

_Craspedopoma_, 298, _414_

_Craspedostoma_, _408_

_Crassatella_, _451_

_Cratena_, _432_

Crawling of _Helix_, 45

_Cremnoconchus_, 16, 302, _413_

_Crenatula_, 75, _449_

_Crenella_, _449_

_Crenipecten_, _450_

_Crepidula_, =248=, 257, =412=, _412_; parasitic, =78=

_Crepipatella_, =248=, _412_

_Creseis_, =436=, _436_; eyes, 186

_Crimora_, _434_; radula, 229

_Crioceras_, 247, =399=, _399_

_Cristigibba_, 311, 319, 320, _441_

_Crossostoma_, _408_

_Crucibulum_, =248=, _412_

_Cryptochiton_, 245, 371, 402, _404_

_Cryptochorda_, _425_

_Cryptoconchus_, _404_

_Cryptophthalmus_, _430_

_Cryptostracon_, 353, _441_

Ctenidia, 151--_see_ Branchiae

_Ctenopoma_, 346–351, _414_

_Cucullaea_, 274, _448_

_Cultellus_, _457_

_Cuma_, _423_

_Cumingia_, _453_

_Cuspidaria_, _459_; branchiae, 168

_Cuvierina_, =436=, _436_

_Cyane_, _410_

_Cyathopoma_, =247=, 268, 314, 338, _414_

_Cyclas_, _453_; veliger, =132=; ova, 146; otocyst, =197=; _C. cornea_, thread-spinning, 29; distribution, 282

_Cyclina_, _454_

Cyclobranchiata, 156

_Cyclocantha_, _409_

_Cyclomorpha_, _414_

_Cyclonassa_, _423_

_Cyclonema_, _409_

Cyclophoridae, origin, 21

_Cyclophorus_, 302, =306=-319, 329–334, 344, 352–358, _414_; jaws, =212=; radula, =21=

_Cyclostoma_, 328, 331–338, =414=, _414_; stomach, 239; vision, 184; osphradium, 195; nervous system, =205=; _C. elegans_, 287, 288

Cyclostomatidae, origin, 21; radula, 224; gait, 199

_Cyclostrema_, _408_

_Cyclosurus_, =247=, 337, _414_

_Cyclotopsis_, 338, _414_

_Cyclotus_, 296, 319, 320, _414_

_Cylichna_, =428=, _430_; radula, 215

_Cylindrella_, =247=, =260=, 278, 343–355, =348=, _442_; monstrosity, 251, =252=

Cylindrellidae, radula, 233, =234=

_Cylindrites_, _430_

_Cylindrobulla_, _430_

_Cylindromitra_, _425_; radula, 222

_Cymbium_, 255, 367, _425_; radula, =221=

_Cymbulia_, _437_

_Cymbuliopsis_, _437_

_Cynodonta_, _424_

_Cyphoma_, _419_

_Cypraea_, =178=, _419_; prices given for rare, 122; mantle-lobes, 177, =178=; radula, =224=; shell, =255=, 260, =261=; _C. moneta_, 96

_Cypraecassis_, _420_

_Cypraedia_, _419_

_Cypraeovula_, _419_

_Cyprimeria_, _454_

_Cyprina_, _451_

_Cyrena_, 15, _453_; distribution, 285, 294

_Cyrenella_, _453_

_Cyrtia_, _505_; stratigraphical distribution, 507, 508

_Cyrtoceras_, _394_

_Cyrtodaria_, _457_

_Cyrtodonta_, _452_

_Cyrtolites_, _407_

_Cyrtonotus_, _448_

_Cyrtotoma_, _414_

_Cysticopsis_, 346–351, _441_

_Cystiscus_, _425_

_Cystopelta_, 325, 326, _440_

_Cytherea_, =454=, _454_

_Dacrydium_, _449_

_Daedalochila_, _441_

Dall, W. H., quoted, 35; on branchiae, 164

_Damayantia_, _440_

_Daphnella_, _426_

Darbyshire, R. D., on tenacity of life, 39

_Dardania_, _415_

Dart-sac, 142

_Daudebardia_, =289=, 292 f., _440_

_Davidsonia_, _505_, 508

_Dawsonella_, _410_

_Dayia_, _505_, 508

Decapoda, _385_ f.

Decollation, 260

Deep-sea Mollusca, 374

De Folin, experiment on _Cyclostoma_, 157

_Deianira_, _410_

Delage, experiments on otocysts, 197

_Delphinula_, _409_

Deltidium, 499

_Dendronotus_, _433_; protective coloration, 72; habits, 51

_Dentalium_, =6=, =444=, _445_; used as money, 97; veliger, =131=; radula, =228=

_Dentellaria_, =350=-355, _441_; aperture, =63=

Desert species, 25, 85

_Deshayesia_, _411_

_Desmoulea_, _423_

Development of fertilised ovum, 130 f.

_Dexiobranchaea_, _437_

_Diadema_, _414_

_Diala_, _415_

_Dialeuca_, _441_

_Diaphora_, 314

_Diaphorostoma_, _412_

_Diastema_, _418_

_Diastoma_, _417_

_Diaulula_, _434_

_Dibaphus_, _425_

Dibranchiata, _380_; eye, 183; nervous system, 207

_Diceras_, 269, _455_

_Didaena_, =12=, 297, _455_

Differences of sex, 133

_Dignomia_, 511

Digonopora, 134, 144

_Diloma_, _408_

_Dimorphoptychia_, _410_

_Dimya_, _450_

_Dinobolus_, _504_, 508

_Dinoplax_, _403_

Ditocardia, 9, 170, _405_ f.

_Diplodonta_, _452_

_Diplommatina_, 302–327, _413_

_Diplomphalus_, 322, 323, _440_

_Diplopoma_, 346, 351, _414_

_Dipsaccus_, _424_

_Dipsas_, 307

_Discina_, 464, 468, 471, 475, _487_; distribution, 485; fossil, 493, _504_; stratigraphical distribution, 506, 508

Discinidae, _487_, 496, _504_, 508, 511

_Discinisca_, _487_, 510; distribution, 485, 486

_Discites_, _395_

_Discodoris_, _434_

_Discosorus_, _394_

_Distortio_, 255--see _Persona_

_Ditropis_, 312, 314, _414_

Docoglossa, 227, _405_

_Dolabella_, =428=, _431_

_Dolabrifer_, _431_

_Dolium_, _419_; acid secretion, 237

_Donax_, 269, 446, _453_

_Dondersia_, _404_

_Dorcasia_, 333, _441_

_Doridium_, _430_

_Doridunculus_, _434_; radula, 229

_Doriopsis_, _434_

_Doris_, breathing organs, =159=; radula, 230

_Dorsanum_, _423_

_Dosidicus_, _390_

_Dosinia_, _454_

_Doto_, _433_; protective coloration, 71

_Dreissensia_, =14=, 123, _452_; hibernation, 26; singular habitat, 48; veliger, =132=, 146; eyes, 192

_Dreissensiomya_, _452_

_Drepania_, _434_

_Drillia_, _426_

_Drymaeus_, 356, _442_

_Dryptus_, 356, _441_

_Durgella_, 301, 304, _440_

Dwarf varieties, 88

_Dybowskia_, 290

_Eastonia_, _454_

_Eburna_, =267=, _424_; radula, =220=

Ecardines, 466; muscles, 476; fossil, 493; families, _487_, _503_, 508

_Eccyliomphalus_, _413_

_Echinospira_, 133

_Edentulina_, 338

Egg-laying of _Arion_, =42= f.; of Mollusca generally, 123

_Eglisia_, _411_

Eider-duck, shells used by, 102

_Elaea_, 322, _440_

_Elasmoneura_, _411_

_Eledone_, =385=, _385_; radula, 236

_Elizia_, _456_

_Elysia_, _432_; protective coloration, 73; breathing, 152; radula, 217, =230=, =432=

_Emarginula_, =265=, _406_

_Embletonia_, 429

_Emmericia_, _415_

_Ena_, 296, _442_

_Enaeta_, _425_

_Endoceras_, _394_

_Endodonta_, 325, 334, _441_

_Engina_, _424_

_Enida_, _408_

_Ennea_, 298, 302, 306, 309, 314, 316, 328–337, =440=, _440_; habits, 54; _E. bicolor_, 279

_Enoplochiton_, =403=, _403_

_Enoploteuthis_, _391_

_Ensis_, _457_

_Entocolax_, 77, 79, 152

_Entoconcha_, 77, 79, 152, 216

_Entovalva_, 77, 82

_Ephippodonta_, _453_; commensal, =81=

_Epidromus_, _420_

Epiphragm, 26, 27 f.

Epipodia, 427

_Erato_, _419_

_Eremophila_, 294

_Ergaea_, =248=, _412_

_Erinna_, 327, _439_

Erosion, 276

_Ervilia_, _454_

_Erycina_, _453_

Escargotières, 119

_Estria_, 329, _440_

Estuarine species, 14

_Ethalia_, _409_

_Eucalodium_, 260, 353, _442_

_Euchelus_, _408_

_Euchrysallis_, _420_

_Eudioptus_, _442_

_Eudoxochiton_, _403_

_Euhadra_, 316, 318, _441_

Eulamellibranchiata, _451_; gill, =166=, 167

_Eulima_, _422_; parasitic, 77, =79=

_Eulimella_, 250, _422_

_Eulota_, 296, _441_

_Euomphalus_, 247, _413_

_Euplecta_, _440_

_Eupleura_, _423_

_Euplocamus_, _434_

_Eurybia_, _438_

_Eurycampta_, 346–351

_Eurycratera_, 349, 351, _441_

_Eurystoma_, 304

_Eurytus_, _442_

_Euthria_, _424_

Euthyneura, 203

_Eutrochatella_, 347–351, =348=, _410_

Exploring expeditions, 362

Eye in Mollusca, 181 f.

_Facelina_, _432_

_Fasciolaria_, _424_; radula, =221=

_Fastigiella_, _416_

_Favorinus_, _432_

_Fenella_, _415_

Fertilised ovum, development, 130 f.

_Ferussacia_, 291, 293, 297 f., _442_

Fiji islanders, use of shells, 98

Filibranchiata, _448_; gill, =166=

_Fiona_, _432_; radula, 217

_Firoloida_, _421_

Fischer and Bouvier, on breathing of _Ampullaria_, 158

_Fischeria_, 15, 328, _453_

Fish devour Mollusca, 59

_Fissurella_, =265=, _406_; breathing organs, =153=; apical hole, 156; nervous system, 204; radula, 227; growth, =261=

_Fissurellidaea_, _406_

_Fissuridea_, _406_

_Fissurisepta_, _406_

_Fistulana_, 262, _457_

_Flabellina_, _432_

_Fluminicola_, _415_

_Folinia_, _415_

Food of Mollusca, 30 f.; Mollusca as food, 102 f.

Foot, 198; in classification, 5

Forel, on deep-water _Limnaea_, 162

Formation of shell, 255

_Fortisia_, _429_

_Fossarina_, _413_

_Fossarulus_, 302, _415_

_Fossarus_, _413_

Fourth orifice in mantle, 174

Fresh-water species living in sea, 12; frozen hard, 24

Frogs and toads devour Mollusca, 58

_Fruticicola_, 285, 290, 316, 318, _441_

_Fruticocampylaea_, 296

_Fryeria_, _434_

_Fulgur_, =249=, _424_

_Fusispira_, _420_

_Fusus_, 262, _424_

_Gadinia_, =152=, _431_; breathing, 18, 151; classification, 19; radula, 217, =230=

Gain, W. A., quoted, 32, 33, 39; on taste of Mollusca, 179

_Galatea_, 15, 328, 336, _453_

_Galeomma_, 175, _453_

_Galerus_, =248=, _412_; egg-capsules, 125

Garstang, W., on protective and warning coloration, 73

Gaskoin, on tenacity of life, 38; on egg-laying, 42

Gassies, on hybrid union in snails, 130

Gasteropoda, on classification, 8, 11, 400 f.

_Gastrana_, _453_

_Gastrochaena_, _457_; habits, 64

_Gastrodonta_, _440_

_Gastropteron_, 245, _430_

_Gaza_, 376, _408_

_Gena_, 246, _408_

_Genea_, _424_

_Genotia_, _426_

_Geomalacus_, =160=, 288, 291, _441_; protective coloration, 70

_Geomelania_, 16, 348, 351, _414_

_Georgia_, 331, _414_

_Georissa_, 318, _410_

_Geostilbia_, 338, _442_

_Gerontia_, _441_

_Gerstfeldtia_, 290

_Gibbula_, _408_

_Gibbus_, 328–=338=, =440=, _440_

_Gillia_, _415_

Gills--_see_ Branchiae

_Girasia_, 301, 304, _440_

_Glandina_, =54=, =178=, 278, 292 f., 339–355, _440_; radula, 231, =232=; habits, 53

Glands, germ, 134, 140; nidamental, 136

_Glassia_, 501, _505_

_Glaucomya_, 320, _454_

_Glaucus_, 429, _432_

_Gleba_, _437_

_Glessula_, 301, 309, 310, 333, _442_

Glochidium, =147=

_Glomus_, _448_

_Glossoceras_, _394_

Glossophora, 7

_Glottidia_, distribution, 485, _487_

_Glycimeris_, _457_

_Glyphis_, _406_

_Glyptostoma_, 341, _441_

_Gomphoceras_, _394_, =395=

_Gonatus_, _391_

_Goniatites_, _397_, =398=

_Goniobasis_, 341, _417_

_Goniodoris_, _434_; protective coloration, 73; radula, 229

_Goniomya_, _458_

_Gonostoma_, 291, 316, _441_

_Goniostomus_, _442_

_Grammysia_, _459_

_Grateloupia_, _454_

Great _Eastern_ and mussels, 116

Greenhouses, slugs in, 35

Green oysters, 108

_Gresslya_, _458_

Growth of shell, 40, 257

_Guesteria_, _440_

_Guildfordia_, _409_

_Guivillea_, 186, 376, _425_

Gulls and Mollusca, 56

_Gundlachia_, 19, 325, 345, 352, 359, _439_

Gymnoglossa, 216, 225, _422_

Gymnosomata, _437_

_Gyroceras_, 247, _395_

_Gyrotoma_, _417_

_Hadra_, 306, 315, 319–325, =322=, _441_

_Hadriania_, _423_

Haemoglobin, 171

_Hainesia_, 336, _414_

_Halia_, 366, _426_

_Haliotinella_, _431_

_Haliotis_, =266=, _407_; and coyote, 57; holes of, 156; osphradium, 195; epipodium, 199; nervous system, 204; radula, 215, 226

_Halopsyche_, 159, =438=, _438_

_Haminea_, =428=, _430_; protective coloration, 73

_Hamites_, _399_

_Hamulina_, _399_

_Hanleyia_, _403_

_Hapalus_, 331, _442_

_Harpa_, radula, _425_, 216, 221; self-mutilation, 45

_Harpagodes_, _418_

_Harpoceras_, _399_

_Harvella_, _454_

Hatching of eggs, 43

Hazay, on duration of life, 39; on variation in _Limnaea_, 93

Hearing powers of Mollusca, 196

Heart, in classification, 9;

## action during hibernation, 26;

and branchiae, =169=

Hectocotylus arm, 137 f.

_Helcion_, _405_; protective coloration, 69

_Helcioniscus_, _405_

Hele, F. M., on _Hyalinia_, 33; on _Stenogyra_, 34

_Helicarion_, 309, 316, 325, 332, _440_; radula, 232; habits, 45, 67

Helicidae, radula, 232, =234=

_Helicina_, 305, 306, 316–327, 338–358, _410_; origin, =21=; exterminated by cold, 24

_Helicophanta_, 335, =336=, =441=, _441_

_Heligmus_, _449_

_Helix_, _441_; toothed aperture, 63; protective coloration, 70; variation, 87; carbonic acid, 163; eye, =181=, =183=; food, 179; smell, 194; jaw, =211=; distribution, 285; tenacity of life, 37; breeding, 129

_Helix alternata_, =340=; _angulata_, =350=; _aperta_, 38, 39, 51, =293=; _arbustorum_, bathing, 23; _caperata_, variation, 89; _cereolus_, =340=; _cicatricosa_, =316=; _crenilabris_, 45; _delphinuloides_, =297=; _desertorum_, 37, 38, 70, 294; _fidelis_, =341=; _haemastoma_, habits, 70; _harpa_, 287; _hortensis_, =10=, 279; pulsations, 26; epiphragm, 28; rock-boring, 49; dart, =143=; _imperator_, =347=; habits, 45; _laciniosa_, =297=; _lactea_, 25, 38, 42, 279; _lima_, =350=; _muscarum_, =347=; _nemoralis_, 38, =180=; _niciensis_, =292=; _nux denticulata_, =350=; _palliata_, =340=; _pisana_, 25; habits, 33; _pomatia_, 25, 34, 40; eye, =181=; _pomum_, =322=; _pulchella_, 279; _richmondiana_, =322=; _rosacea_, =259=; _rostrata_, =347=; _rota_, =314=; _rufescens_, pulsations, 26; _similaris_, 279; _souverbiana_, =336=, =441=; _strigata_, =293=; _tristis_, habits, 49; _turricula_, =297=; _Veatchii_, 38; _Waltoni_, =304=; _Wollastoni_, =297=; _zonata_, =293=

_Helix aspersa_, homing, 35; smell, 36; duration of life, 39; growth, 40; strength, 45; boring rock, 50; variation, 87, 89; eaten, 119; hybrid union, 130; generative organs, 140 f., =141=; dart-sac, =143=; pulmonary chamber, 160; radula, 217; alimentary canal, =237=; monstrosities, 251, =252=; growth, 258; distribution, 279, 289

_Hemiarthrum_, _403_

_Hemicardium_, _455_

_Hemidonax_, _453_

_Hemifusus_, _424_

_Hemipecten_, _450_

_Hemiplecta_, 310, 316, 319, 321, _440_

_Hemisepius_, _389_

_Hemisinus_, 357, _417_

_Hemitoma_, =265=

_Hemitrichia_, 314

_Hemitrochus_, 346–351, _441_

_Hemphillia_, 245, 341, _441_

_Hercoceras_, _395_

Herdman, Prof. W. A., on cerata of Nudibranchs, 71 f.; experiments on taste of Nudibranchs, 72; on _Littorina rudis_, 151 n.

_Hermaea_, _432_; protective coloration, 73

Hermaphrodite Mollusca, 134, 140, 145

Hermit-crabs, shells used by, 102

_Hero_, _432_

_Heterocardia_, _454_

_Heterodiceras_, _455_

Heteropoda, 9, _420_ f.; radula, 228; foot, 200

_Heudeia_, 316, _410_

_Hexabranchus_, _434_

Hibernation, 25, 163

High altitudes, Mollusca living at, 24

_Himella_, 15

_Hindsia_, _424_

_Hindsiella_, _453_

Hinge area, 493, 498

Hinge, in bivalves, 272

_Hinnites_, 257, _450_

_Hipponyx_, 248, _412_

_Hippopus_, _455_

_Hippurites_, =455=, _456_

_Histiopsis_, _391_

_Histioteuthis_, _391_

_Holcostoma_, _417_

_Holohepatica_, _433_

_Holopella_, _411_

_Holospira_, 339, 353, _442_

Holostomata, 156

_Homalogyra_, _413_; radula, 223

_Homalonyx_, 245, =343=-358, _443_

Homing powers of Mollusca, 34

_Homorus_, 330–337, _443_

_Hoplites_, _399_

_Hoplopteron_, _422_

_Horea_, 332

_Horiostoma_, _409_

Hot springs, Mollusca living in, 25

_Huronia_, _394_

_Hyalaea_, =10=, _436_

_Hyalimax_, 245, 305, 306, 338, _443_

Hyaline stylet, 240

_Hyalinia_, _440_; pulsations, 26; food, 33; smell, 194; dart, =143=; radula, 232, =234=; distribution, 287 f., 318, 340–357; _H. alliaria_, 279; smell, 194; _cellaria_, 279; _Draparnaldi_, 33

_Hyalocylix_, _437_

_Hyalosagda_, 352

_Hybocystis_, =305=, 309, _414_

Hybridism, 129

_Hydatina_, _430_; radula, =231=

_Hydrobia_, 325, 332, _415_; _H. ulvae_, egg-laying, 128

_Hydrocena_, 298, _410_; radula, 226

Hymenoptera build in dead shells, 102

_Hypobranchaea_, _434_; radula, 230

_Hypotrema_, _448_

_Hypselostoma_, 248, =302=, 305, 314, _442_

_Hyria_, 344, _452_

_Hystricella_, 297

_Ianthina_, 360, =126=, _411_; egg-capsules, 125; eyes, 186; radula, =224=

_Iapetella_, _385_

_Iberus_, 285–=293=, =297=, _441_

_Ichthyosarcolites_, _456_

_Idalia_, =179=, 429, _434_; radula, 229, 230

_Idas_, _449_

_Idiosepion_, _389_

_Illex_, _390_

_Imbricaria_, _425_; radula, =221=

_Imperator_, _409_

Indians of America, use of shells, 100

_Infundibulum_, _408_

_Inioteuthis_, _389_

Ink-sac, =241=

_Inoceramus_, _449_

Insects eaten by Mollusca, 32

_Insularia_, 319, 320

Intestine, 241

_Io_, =16=, 340, _417_

_Iopas_, _423_

_Iphigenia_, 15, _453_

_Iravadia_, 305, _415_

_Iridina_, 294

_Irus_, 297

_Isanda_, _409_

_Ischnochiton_, _403_

_Isidora_, 298, 320–327, 333, 336, 359, _439_

_Ismenia_, _404_

_Isocardia_, 269, =451=, _451_

_Isodonta_, _453_

_Isomeria_, 343, 356, _441_

_Issa_, _434_

_Jamaicia_, _414_

_Janella_, =161=, _443_; pulmonary orifice, =161=

Janellidae, radula, 234; distribution, 321–326

_Janus_, _432_

_Japonia_, 318

Jaws, 210

_Jeanerettia_, 346–351, _441_

Jeffreys, Dr., on _Limnaea_, 34; on _Neptunea_, 193

_Jeffreysia_, _415_; radula, 223

_Jorunna_, protective coloration, 73

_Jouannettia_, _457_

_Jullienia_, 307, _415_

_Jumala_, _424_

_Kaliella_, 301, 304, 310, 314–317, 335, _440_

_Kalinga_, _434_

Kashmir, land Mollusca, 280

_Katherina_, _403_

_Kelletia_, _424_

_Kellia_, _453_

_Kellyella_, _452_

Kidneys, 242

King, R. L., on smell in bivalves, 195

_Kingena_, _506_, 508

Kitchen-middens, 104

_Koninckella_, _505_; stratigraphical distribution, 507, 508

_Koninckina_, _505_; stratigraphical distribution, 507, 508

Koninckinidae, 501, _505_, 508

_Kutorgina_, _504_; stratigraphical distribution, 506, 508; embryonic shell, 509

Labial palps, 210

_Labyrinthus_, 342, 353–357, _441_; aperture, =63=

Lacaze-Duthiers on _Testacella_, 52 f.; on smell in _Helix_, 194

_Lacuna_, _413_

_Lacunopsis_, 332

_Lagena_, _424_

_Lagochilus_, 309, 316–319, _414_

_Lamellaria_, 245, _411_; habits and protective coloration, 74; parasitic, 78; radula, 223

_Lamellidoris_, _434_; radula, 229, 230, =231=

_Lampania_, _417_

Land Mollusca, origin, 11 f.

_Lanistes_, 249, 294, 328, 331, _416_

Lankester, Prof. E. Ray, on shell-gland, 132; on haemoglobin, 171

_Lantzia_, 278, 338, _439_

_Laoma_, _441_

_Larina_, 302, _417_

Larvae of Pelecypoda, 7; of insects resembling Mollusca, 67 f.

_Lasaea_, _453_

_Latia_, 19, 326, _439_

_Latiaxis_, _423_

_Latirus_, _424_

Latter, O. H., on _Glochidium_, 147

Layard, E. L., on self-burying Mollusca, 41; on sudden appearance of _Stenogyra_, 47; on _Coeliaxis_, 49; on _Rhytida_ and _Aerope_, 54

_Leda_, _447_

_Leia_, 348–351, _442_

_Leila_, 344, _452_

_Leonia_, _414_

_Lepeta_, _405_

_Lepetella_, _405_

Lepetidae, radula, 227

_Lepidomenia_, _404_; radula, 229

_Leptachatina_, 327

_Leptaena_, 500, 501, 502, =503=, _505_; stratigraphical distribution, 507, 508

_Leptaxis_, _441_

_Leptinaria_, 357, 358, _442_

_Leptochiton_, _403_

_Leptoconchus_, 75, _423_

_Leptoloma_, 348, 351

_Lepton_, _453_; parasitic, 77; commensal, 80; mantle-edge, 175, 178

_Leptoplax_, _403_

_Leptopoma_, 316, 319, 338, _414_

_Leptoteuthis_, _390_

_Leptothyra_, _409_

_Leroya_, 331

_Leucochila_, _442_

_Leucochloridium_, =61=

_Leucochroa_, =292=, 295, _441_

_Leuconia_, _439_

_Leucotaenia_, 335, 359, _441_

_Leucozonia_, 64, =424=, _424_

_Levantina_, 295

_Libania_, 295

_Libera_, 327, _441_; egg-laying, 128

_Libitina_, _451_

_Licina_, _414_

Life, duration of, in snails, 39

Ligament, 271

_Liguus_, 349, 351, _442_

_Lima_, 178, =179=, _450_; habits, 63

Limacidae, radula, 232

_Limacina_, 59, 249, =436=, _436_

_Limapontia_, 429, _432_; breathing, 152

_Limax_, 245, _440_; food, 31, 179; variation, 86; pulmonary orifice, 160; shell, 175; jaw, =211=; radula, 217; distribution, 285, 324; _L. agrestis_, eats May flies, 31; _arborum_, slime, 30; food, 31; _flavus_, food, 33, 36; habits, 35, 36; _gagates_, 279, 358; _maximus_, =32=, =161=; eats raw beef, 32; cannibalism, 32; sexual union, 128; smell, 193 f.

_Limea_, _450_

_Limicolaria_, 329–332, _443_

_Limnaea_, _439_; self-impregnation, 44; development and variation, 84, 92, 93; size affected by volume of water, 94; eggs, 124; sexual union, 134; jaw, 211; radula, 217, =235=; _L. auricularia_, 24; _glutinosa_, sudden appearance, 46; _Hookeri_, 25; _involuta_, 82, 278, 287; _peregra_, =10=, =180=; burial, 27; food, 34, 37; variation, =85=; distribution, 282; _palustris_, distribution, 282; _stagnalis_, food, 34, 37; variation, =85=, =95=; circum-oral lobes, 131; generative organs, =414=; breathing, 161; nervous system, =204=; distribution, 282; _truncatula_, parasite, 61; distribution, 282

_Limnocardium_, _455_

_Limnotrochus_, 332, _415_

_Limopsis_, _448_

Limpet-shaped shells, 244

Limpets as food for birds, 56; rats, 57; birds and rats caught by, 57; as bait, 118

_Lingula_, 464, 467, 468, 471, =472=, 473, 475, 477, 478, _487_; habits, =483=, 484; distribution, 485; fossil, 493, =494=, _503_; stratigraphical distribution, 506, 508, 510, 511

_Lingulella_, 493, _503_; stratigraphical distribution, 506, 508, 511

_Lingulepis_, _503_, 511

Lingulidae, 485, 487, 496, _503_, 508

_Linnarssonia_, _504_; stratigraphical distribution, 506, 508

_Lintricula_, _426_

_Liobaikalia_, 290

_Liomesus_, _424_

_Lioplax_, 340, _416_

_Liostoma_, _424_

_Liostracus_, _442_

_Liotia_, _408_

_Liparus_, 324, 359, _441_

_Lissoceras_, _399_

_Lithasia_, 340, _417_

_Lithidion_, _414_

_Lithocardium_, _455_

_Lithodomus_, _449_

_Lithoglyphus_, 294, 296, 297, _415_

_Lithopoma_, _409_

_Lithotis_, 302, _443_

_Litiopa_, 30, 361, _415_

_Littorina_, _413_; living out of water, 20; radula, =20=, 215; habits, 50; protective coloration, 69; egg-laying, 126; hybrid union, 130; monstrosity, =251=, =252=; operculum, =269=; erosion, 276; _L. littorea_, in America, 374; _obtusata_, generative organs, =135=; _rudis_, 150; Prof. Herdman’s experiments on, 151 n.

_Littorinida_, _415_

_Lituites_, 247, _395_

Liver, 239; liver-fluke, 61

_Livinhacea_, 333, 359, _441_

_Livona_, _408_; radula, 226; operculum, =268=

Lloyd, W. A., on _Nassa_, 193

_Lobiger_, _432_

_Lobites_, _397_

_Loligo_, 378–_389_; glands, 136; modified arm, 139; eye, =183=; radula, 236; club, =381=; _L. punctata_, egg-laying, 127; _vulgaris_, larva, 133

_Loligopsis_, _391_

_Loliguncula_, _390_

_Loliolus_, _390_

_Lomanotus_, _433_

_Lophocercus_, _432_

_Lorica_, _403_

Lowe, E. J., on growth of shell, 40

_Loxonema_, _417_

_Lucapina_, _406_

_Lucapinella_, _406_

_Lucerna_, _441_

_Lucidella_, 348–351, _410_

_Lucina_, =270=, _452_

_Lucinopsis_, _454_

Lung, 151, 160

_Lunulicardium_, _455_

_Lutetia_, _452_

_Lutraria_, 446, _456_

_Lychnus_, _442_

_Lyonsia_, _458_

_Lyonsiella_, _458_; branchiae, 168

_Lyra_, stratigraphical distribution, 507

_Lyria_, _425_

_Lyrodesma_, _447_

_Lysinoe_, _441_

_Lytoceras_, _398_

_Maackia_, 290

_Macgillivrayia_, 133

_Machomya_, _458_

_Maclurea_, _410_

_Macroceramus_, 343–353, _442_

_Macroceras_, _440_

_Macrochilus_, _417_

_Macrochlamys_, 296, 299, 301 f., 310, 316–322, _440_

_Macrocyclis_, 358, =359=, _442_

_Macron_, _424_

_Macroön_, _441_

_Macroscaphites_, 247, =399=, _399_

_Macroschisma_, =265=, _406_

_Mactra_, 271, 446, _454_

_Macularia_, 285, 291, =292= f., _441_

_Magas_, _506_; stratigraphical distribution, 507, 508

_Magellania_, 500

_Magilus_, =75=, _423_

_Mainwaringia_, 302

_Malaptera_, _418_

_Malea_, _419_

_Malletia_, _447_

_Malleus_, _449_

_Mangilia_, _426_

Mantle, 172 f., =173=; lobes of, 177

_Margarita_, _408_; radula, =225=

_Marginella_, _425_; radula, 221

_Mariaella_, 314, 338, _440_

_Marionia_, _433_

_Marmorostoma_, _409_

Marrat, F. P., views on variation, 82

_Marsenia_, 133

_Marsenina_, _411_

_Martesia_, 305, _457_

_Mastigoteuthis_, _390_

_Mastus_, 296, _442_

_Matheronia_, _455_

_Mathilda_, 250, _417_

_Maugeria_, =403=

_Mazzalina_, _424_

_Megalatractus_, _424_

Megalodontidae, _451_

_Megalomastoma_, 344, _414_

_Megalomphalus_, _416_

_Megaspira_, 358, _442_

_Megatebennus_, _406_

_Megerlia_, distribution, 486, _487_

_Meladomus_, 249, 328, 331, _416_

_Melampus_, =18=, 199, 250, =439=, _439_

_Melanatria_, 336

_Melania_, =276=, =417=, _417_; distribution, 285, 292 f., 316 f., 324, 336

_Melaniella_, _442_

Melaniidae, origin, 17

Melanism in Mollusca, 85

_Melanopsis_, _417_; distribution, 285, 291, 292 f., 323, 326

_Melantho_, 340, _416_

_Melapium_, _424_

_Meleagrina_, _449_

_Melia_, 348

_Melibe_, _432_

_Melongena_, _424_; radula, =220=; stomach, =238=

_Merica_, _426_

_Merista_, _505_, 508

_Meroe_, _454_

_Merope_, 327

_Mesalia_, _417_

_Mesembrinus_, 356, _442_

_Mesodesma_, _454_

_Mesodon_, =340=, _441_

_Mesomphix_, 340, _440_

_Mesorhytis_, 377

_Meta_, _423_

_Metula_, _424_

_Meyeria_, _424_

_Miamira_, _434_

_Microcystis_, 323, 324, 327, 338, _440_

_Microgaza_, _408_

_Micromelania_, 12, 297

_Microphysa_, protective habits, 70

_Microplax_, _403_

_Micropyrgus_, _415_

_Microvoluta_, _425_

_Middendorffia_, _403_

_Milneria_, _451_

Mimicry, 66

_Minolia_, _408_

_Mitra_, _425_; radula, 221

_Mitrella_, _423_

_Mitreola_, _425_

_Mitrularia_, =248=, _412_

_Modiola_, 446, _449_; habits, 64; genital orifice, 242

_Modiolarca_, _449_

_Modiolaria_, _449_; habits, 78

_Modiolopsis_, _452_

_Modulus_, _417_

_Monilia_, _408_

Monkey devouring oysters, 59

_Monoceros_, _423_

_Monocondylaea_, _452_

_Monodacna_, 12, 297, _455_

_Monodonta_, _408_, =408=; tentaculae, =178=

_Monogonopora_, 134, 140

_Monomerella_, 496, _504_

_Monopleura_, _456_

_Monotis_, _449_

Monotocardia, 9, 170, _411_

Monstrosities, 250

_Montacuta_, _452_; _M. ferruginosa_, commensal, 80; _substriata_, parasitic, 77

_Mopalia_, _403_

Moquin-Tandon, on breathing of Limnaeidae, 162; on smell, 193 f.

_Moreletia_, _440_

_Morio_, _420_

_Mormus_, 356, _442_

Moseley, H. N., on eyes of _Chiton_, 187 f.

_Moussonia_, 327

Mouth, 209

_Mucronalia_, _422_

Mucus, use of, 63

_Mulinia_, =272=

_Mülleria_, 344, _452_

_Mumiola_, _422_

_Murchisonia_, 265, _407_

_Murchisoniella_, _422_

_Murex_, _423_; attacks _Arca_, 60; use of spines, 64; egg-capsules, 124; eye, =182=; radula, =220=; shell, =256=

Musical sounds, 50

Mussels, cultivation of, 115; as bait, 116; poisonous, 117; on _Great Eastern_, 116

_Mutela_, 294, 328, 331, 336, _452_

_Mutyca_, _425_

_Mya_, 271, 275, =446=, _456_; stylet, 240; _M. arenaria_, variation, 84

Myacea, _456_

_Myalina_, _449_

_Mycetopus_, 307, 316, 344, _452_

_Myochama_, =458=

_Myodora_, _458_

_Myophoria_, _448_

Myopsidae, _389_

_Myrina_, _449_

_Myristica_, _424_

Mytilacea, _448_

_Mytilimeria_, _458_

_Mytilops_, _452_

_Mytilopsis_, 14

_Mytilus_, 258, _449_; gill filaments, =166=, 285; _M. edulis_, =14=, =165=; attached to crabs, 48, 78; pierced by _Purpura_, =60=; Bideford Bridge and, 117; rate of growth, 258; stylet, 240

_Myxostoma_, _414_

_Nacella_, _405_

_Naiadina_, _449_

_Nanina_, 278, 300 f., 335, _440_; radula, 217, 232

_Napaeus_, 296–299, 316, _442_

_Naranio_, _454_

_Narica_, _412_

_Nassa_, _423_; egg-capsules, =126=; sense of smell, 193

_Nassodonta_, _423_

_Nassopsis_, 332

_Natica_, =246=, 263, _411_; spawn, =126=; operculum, =268=

_Naticopsis_, _409_

‘Native’ oysters, 106

_Nausitora_, 15

Nautiloidea, _393_

_Nautilus_, 254, =392=, _395_; modified arms, 140; eye, =183=; nervous system, 206; radula, 236; kidneys, 242

_Navicella_, 267, 268, 324, 327, _410_; origin, =17=

_Navicula_, =358=, _442_

_Navicula_ (Diatom), cause of greening in oysters, 108

_Nectoteuthis_, _389_

_Neda_, _431_

_Nematurella_, 12, 297

_Nembrotha_, _434_

_Neobolus_, _504_

_Neobuccinum_, _424_

_Neocyclotus_, 357, 358

_Neomenia_, =8=, 133, 216, 228, =404=, _404_; breathing organs, =154=; nervous system, =203=

_Neothauma_, 332

Neotremata, 511

_Neptunea_, 252, 262, _423_; egg-capsules, =126=; capture, 193; monstrosity, =251=

_Nerinea_, _417_

_Nerita_, =17=, _410_; _N. polita_ used as money, 97

Neritidae, 260, _410_; radula, =226=

_Neritina_, =256=, _410_; origin, 16, =17=, =21=; egg-laying, 128; eye, 181; distribution, 285, 291 f., 324, 327; _N. fluviatilis_, habitat, 12, 25

_Neritoma_, _410_

_Neritopsis_, _409_; radula, 226; operculum, =269=

Nervous system, 201 f.

_Nesiotis_, 357, _442_

New Zealanders, use of shells, 99

_Nicida_, _413_

_Ninella_, _409_

_Niphonia_, _408_

_Niso_, _422_

_Nitidella_, _423_

_Nodulus_, _415_

_Notarchus_, _431_

_Nothus_, 358, _442_

_Notobranchaea_, _438_

_Notodoris_, _434_

_Notoplax_, _403_

_Novaculina_, 305

_Nucula_, 254, 269, =273=, _447_

Nuculidae, otocyst, 197; foot, 201

_Nuculina_, _448_

Nudibranchiata, _432_; defined, 10; protective and warning colours, 71 f.; breathing organs, 159

_Nummulina_, 295

_Nuttallina_, _403_

_Obba_, 311, 315, _441_

_Obbina_, 306, 311, 312, =314=, 319

_Obeliscus_, _442_

_Obolella_, 496, _504_; stratigraphical distribution, 506, 508

Obolidae, 496, _504_, 508

_Obolus_, _504_, 508; embryonic shell, 509

_Ocinebra_, _423_

Octopodidae, hectocotylised arm, 137, 139, =140=

_Octopus_, =379=-_386_; egg-capsules, =127=; vision, 184; radula, =236=; crop, 238

_Ocythoe_, _384_; hectocotylus, =138=

_Odontomaria_, _407_

_Odontostomus_, =358=, =442=

_Odostomia_, 250, _422_; parasitic, 78

Oesophagus, 237

_Ohola_, _434_

Oigopsidae, _390_

_Oldhamina_, _506_, 508

_Oleacina_, habits, 55

_Oliva_, =199=, =255=, 275, =425=, _426_

_Olivancillaria_, _426_

_Olivella_, 260, 267, _426_; _O. biplicata_ as money, 97

_Olivia_, _408_

_Omalaxis_, _413_

_Omalonyx_, habitat, 23

_Ommastrephes_, =6=, 378, _390_

Ommatophores, 180, 187

_Omphalotropis_, 306, 309, 316, 324, 327, 338, _414_

_Onchidiella_, _443_

Onchidiidae, 245; radula, 234; anus, 241

_Onchidiopsis_, _411_

_Onchidium_, _443_; breathing, 163; eyes, 187

_Onchidoris_, radula, 230

_Oniscia_, _420_

_Onoba_, _415_

_Onychia_, _390_

_Onychoteuthis_, _390_; club, =386=

_Oocorys_, _420_

_Oopelta_, 329, _440_

_Opeas_, _442_

Operculum, 267 f.

_Ophidioceras_, 247, _395_

_Ophileta_, _413_

_Opis_, _451_

Opisthobranchiata, _427_; defined, 9; warning, etc., colours, 71 f.; generative organs, 144; breathing organs, 158; organs of touch, 178; parapodia, 199; nervous system, 203; radula, 229

_Opisthoporus_, =266=, 300, 314–316, _414_

_Opisthostoma_, 248, =309=, _413_

_Oppelia_, _399_

_Orbicula_, =464=

Orbiculoidea, _504_, 510

Orders of Mollusca, 5–7

Organs of sense, 177

Origin of land Mollusca, 11 f.

_Ornithochiton_, _403_

_Orphnus_, 356, _441_

_Orpiella_, _440_

_Orthalicus_, 342–358, =355=, _442_; habits, 27; variation, 87; jaw, =211=; radula, 233, =234=

_Orthis_, _505_; stratigraphical distribution, 506, 507, 511

_Orthoceras_, =394=, _394_

_Orthonota_, _457_

_Orthothetes_, _505_; stratigraphical distribution, 507, 508

_Orygoceras_, 247

Osphradium, 194 f.

_Ostodes_, 327

_Ostracotheres_, 62

_Ostrea_, 252, 258, 446, _449_; intestine, 241

_Otina_, 18, _439_

_Otoconcha_, 326, _440_

Otocysts, 196 f., =197=

_Otopleura_, _422_

_Otopoma_, 331, 338, _414_

_Otostomus_, 353, _442_

Ovary, 135

Ovoviviparous genera, 123

_Ovula_, _419_; protective coloration, 70, 75; radula, 80, 224; used as money, 97

Ovum, development of fertilised, 130

_Oxychona_, 358

_Oxygyrus_, _422_; foot, 200

_Oxynoe_, _432_; radula, 230

Oyster-catchers, shells used by, 102

Oyster, cultivation, 104–109; living out of water, 110; enemies, 110 f.; reproduction, 112 f.; growth, 114; cookery, 114; poisonous oysters, 114; vision, 190

_Pachnodus_, 329–335, _441_, _442_

_Pachybathron_, _425_

_Pachychilus_, _354_

_Pachydesma crassatelloides_, money made from, 97

Pachydomidae, _451_

_Pachydrobia_, 307, _415_

_Pachylabra_, _416_

_Pachyotus_, 334, =336=, =355=, 358, _441_

_Pachypoma_, _409_

_Pachystyla_, 337, _440_

_Pachytypus_, _451_

_Padollus_, _407_

Palaearctic region, 284 f.

_Palaeoneilo_, _447_

_Palaeosolen_, _457_

_Palaina_, 327, _413_

_Palio_, _434_

Pallial line and sinus, 270

_Pallifera_, 340, _440_

Palliobranchiata, 464

_Paludina_, _416_; penis, 136; eye, 181; vision, 184; _P. vivipara_, 24--see also _Vivipara_

_Paludomus_, 332, 336, 338, _417_

Panama, Mollusca of, 3

_Panda_, 322, 325, 335

_Pandora_, _458_

Papuans, use of shells, 99

_Papuina_, 309, 319–324, _441_

_Paramelania_, 332

_Paramenia_, _404_

Parasitic worms, 60 f.; Mollusca, 74 f.

_Parastarte_, _451_

_Parkinsonia_, =398=

_Parmacella_, 245, 291, 294 f., 438 n., _440_; radula, 232; shell, 175

_Parmacochlea_, 322, 326, _440_

_Parmarion_, 309, _440_

_Parmella_, 326, _440_

_Parmophorus_, _406_

_Parthena_, 349–352, =350=, _441_

Parts of univalve shell, 262; bivalve, 269

_Partula_, 319–327, =326=, _442_; radula, 233

_Paryphanta_, 321, 325, _440_

_Paryphostoma_, _415_

_Passamaiella_, 332

_Patella_, _405_, 464; as food, 56 f.; eye, =182=; radula, =214=, 215, =227=; crop, 238; anus, 241; kidneys, 242; shell, 262; _P. vulgata_, veliger, =132=; breathing organs, etc., 156, =157=

Patelliform shell in various genera, 19

_Paterina_, 509, 510, 511

_Patinella_, radula, 227

_Patula_, 297, 298, 318–338, =340=, _441_

_Paxillus_, _413_

Pearl oysters, 100

_Pecten_, 446, =450=, _450_; organs of touch, 178; ocelli, =191=; flight, 192; nervous system, =206=; genital orifice, 242; ligament, 271

_Pectinodonta_, _405_; radula, 227

_Pectunculus_, _448_

_Pedicularia_, 75, _419_; radula, 224

_Pedinogyra_, 319, 322, _442_

_Pedipes_, =18=, 199, =439=, _439_

_Pedum_, _450_

Pelagic Mollusca, 360

Pelecypoda, _7_, _445_; development, 145; generative organs, 145; branchiae, =166–169=; organs of touch, 178; eyes, 189 f.; foot, 201; nervous system, 205

_Pella_, 333

_Pellicula_, 352, _442_

_Peltoceras_, _399_

_Pentadactylus_, _423_

_Peraclis_, _436_

_Pereiraea_, _418_

_Perideris_, 328–330, _443_

Periodicity in breeding, 129

_Periophthalmus_, 187

Periostracum, 275

_Periploma_, _459_

_Perisphinctes_, _399_

_Perissodonta_, _418_

_Perissolax_, _424_

_Peristernia_, _424_

_Perna_, _449_; ligament, 271

_Pernostrea_, _449_

_Peronaeus_, 358, _442_

_Peronia_, _443_

_Perrieria_, 319, _442_

_Perrinia_, _408_

_Persicula_, _425_

_Persona_ (= _Distortio_), _420_

_Petenia_, 353, _440_

_Petersia_, _420_

_Petraeus_, 295, 331, _442_

_Petricola_, _454_

_Phacellopleura_, _403_

_Phanerophthalmus_, _430_

_Phaneta_, _408_

_Phania_, 312, _441_

_Pharella_, _457_

_Pharus_, _457_

Pharynx, 210

_Phasianella_, _409_

_Phasis_, 333

Phenomena of distribution, 362

_Philine_, 245, =428=, _430_; protective coloration, 73; radula, 229, 230

_Philomycus_, 245, 318, _440_

_Philonexis_, =138=

_Philopotamis_, 304, _417_

_Phoenicobius_, 315, _441_

Pholadacea, _457_

_Pholadidea_, _457_

_Pholadomya_, _459_

_Pholas_, 245, 274, 447, _457_; in fresh water, 15

_Phos_, _424_

_Photinula_, _408_

Phragmophora, _386_

_Phyllidia_, _434_; breathing organs, 159

_Phyllirrhoe_, 360, 428, _433_

_Phyllobranchus_, _432_

_Phylloceras_, =398=, _398_; suture, =396=

_Phylloteuthis_, _390_

_Physa_, _439_; aestivating out of water, 27; spinning threads, 29; sudden appearance, 46; osphradium, 195; nervous system, =205=; radula, =235=; _P. hypnorum_, 23, 27

_Pileolus_, _410_

_Pileopsis_, 76

_Piloceras_, _394_

_Pinaxia_, _423_

_Pineria_, _442_

_Pinna_, _449_; shell, =254=

_Pinnoctopus_, _385_

_Pinnotheres_, 62

_Pinoceras_, _398_

_Pirena_, _417_

_Pirenella_, _416_

_Piropsis_, _424_

_Pirula_--see _Pyrula_

_Pisania_, _424_

_Pisidium_, _453_; smell, 195; ova, 146; _P. pusillum_, distribution, 282

_Pitys_, 327

_Placobranchus_, _432_

_Placostylus_, 322, =323=-325, 359, _442_; radula, 233

_Placuna_, _448_; _P. placenta_ used for windows, 101

_Placunanomia_, _448_

_Placunopsis_, _448_

_Plagioptycha_, 347–351, _441_

_Plagioptychus_, _456_

_Planaxis_, _417_

_Planispira_, 311, 312, 319, _441_

_Planorbis_, 27, 247, _439_; monstrosity, 93; eye, 181; _P. albus_, distribution, 282

_Platyceras_, 76, _412_

_Platydoris_, _434_

Platypoda, _411_

_Platyschisma_, _413_

_Plaxiphora_, _403_

_Plecochilus_, _442_

_Plecotrema_, _439_

_Plectambonites_, _505_

_Plectomya_, _459_

_Plectopylis_, 303, 305, 314, 316; aperture, =63=

_Plectostylus_, 358, _442_

_Plectotropis_, 305, 306, 310, 311, 314–318, _441_

_Plectrophorus_, 298

_Plesiastarte_, _451_

_Plesiotriton_, _420_

_Pleurobranchaea_, 431; jaws, =212=

_Pleurobranchoidea_, _431_

_Pleurobranchus_, 245, =428=, _431_; warning coloration, 73; jaws, =212=; radula, 230

_Pleurocera_, 340, _417_

Pleuroceridae, origin, 17

_Pleurodonta_, 348; aperture, =63=

_Pleuroleura_, _433_

_Pleuromya_, _458_

_Pleurophorus_, _451_

_Pleurophyllidia_, _433_; breathing organs, =159=; radula, 230

_Pleuropyrgus_, _357_

_Pleurotoma_, =426=, _426_; slit, =263=, 265

_Pleurotomaria_, =266=, 373, 376, =407=, _407_; prices given for recent, 122; slit, 156; radula, 226

_Plicatula_, _450_

Pliny the elder, on use of snails, 118, 120

_Plocamopherus_, _434_

_Plochelaea_, _425_

_Plutonia_, 298, _440_

_Pneumoderma_, 158, _437_, =438=

_Poecilozonites_, 352, _440_

Poisonous bite of _Conus_, 65; poisonous oysters, 114; mussels, 117

_Polycera_, _434_; radula, 230

_Polycerella_, _434_

_Polyconites_, _456_

_Polydontes_, 346–351, =347=, _441_

_Polygona_, _424_

_Polygyra_, =340=, 345–353, _441_; aperture, =63=

_Polygyratia_, =246=, 263, 357, _442_

_Polymita_, 346–351, =347=, _441_

Polyplacophora, 9, _401_ f.; radula, 228

_Polytremaria_, =266=, _407_

_Pomatia_, 285, =293=, 295, _441_

_Pomatias_, 288, 289, 292 f., 302, _413_

_Pomatiopsis_, _415_

_Pomaulax_, _409_

_Pompholyx_, 250, 341, _439_

_Ponsonbya_, 332

_Poromya_, _459_; branchiae, 168

_Porphyrobaphe_, 27, 356, _442_

Position of Mollusca in Animal Kingdom, 4

_Potamides_, =16=, _416_

_Potamomya_, _15_

_Potamopyrgus_, 325, 326, _415_

Poterioceratidae, _394_

_Praecardium_, _459_

_Prasina_, _449_

Prices given for rare shells, 121

Primitive mollusc, form of, 245; types of, 7

_Prisogaster_, _409_

_Pristiloma_, 341, _440_

_Proboscidella_, 497, _504_

Productidae, 497, 500, _504_, 508

_Productus_, 492, 501, =502=, _504_; stratigraphical distribution, 508

_Promachoteuthis_, _389_

_Proneomenia_, _404_; breathing organs, 154; nervous system, =203=; radula, 229

_Prophysaon_, 341, _441_; habits, 44

_Propilidium_, _405_

_Proserpina_, =21=, 355, _410_

_Proserpinella_, 354, _410_

Proserpinidae, relationships, 21

Prosobranchiata, _9_, _404_ f.; breathing organs, 154

_Prosocoelus_, _451_

Protective coloration, 69 f.; in snails, 70; in Nudibranchs, 71 f.; in other Mollusca, 74

Protegulum, 509

Protobranchiata, _447_; branchiae, =166=

_Protoma_, _417_

Protremata, 511

_Provocator_, 376, _425_

_Psammobia_, _456_

_Pseudachatina_, 328–330, _443_

_Pseudedmondia_, _452_

_Pseudobalea_, 350

Pseudo-deltidium, 498, 511

_Pseudodon_, 295, 307, _452_

Pseudolamellibranchiata, 167, _449_

_Pseudoliva_, _424_

_Pseudomelania_, _417_

_Pseudomilax_, 296, _440_

_Pseudomurex_, _423_

_Pseudopartula_, 323

_Pseudosubulina_, _440_

Ptenoglossa, 224, _411_

_Pterinaea_, _449_

_Pteroceras_, 256, 262, _418_

_Pteroctopus_, _384_

_Pterocyclus_, =266=, 267, 300, 316, _414_; tube, 157

_Pterodonta_, _418_

Pteropoda, _7_, _434_; breathing organs, 158; foot, 200; radula, 230

_Pterotrachaea_, _421_; foot, 200; radula, =227=

_Ptychatractus_, _424_

_Ptychoceras_, _399_

_Ptychodesma_, _452_

_Pugilina_, _424_

Pulmonata, 10, 22, 151, 185, _438_; origin, 17, 19; breathing organs, 160; nervous system, 203

_Pulsellum_, _444_

_Punctum_, _441_

_Puncturella_, =265=, _406_

_Pupa_, 289, 296, 325–357, _442_; _P. cinerea_, hybrid union, 129

Pupidae, radula, 233

_Pupilla_, _442_

_Pupillaea_, _406_

_Pupina_, 157, 266, 309, 318–327, _414_

_Pupinella_, 318, _414_

_Purpura_, _423_; operculum, =269=; erosion, 276; _P. coronata_, 367; _lapillus_, feeding on _Mytilus_, 60; on oysters, 111; protective coloration, 69; variation, =90=; egg-capsules, 124; time of breeding, 129; distribution, 363 n.

_Purpuroidea_, _423_

_Pusionella_, _426_

_Pygocardia_, _451_

_Pygope_, 497

_Pyramidella_, _422_

Pyramidellidae, 262

_Pyrazus_, 50, _416_

_Pyrgina_, 330

_Pyrgula_, _415_

_Pyrochilus_, _441_

_Pyrolofusus_, _423_

_Pyrula_ (= _Pirula_), _419_, =420=; spawn, =125=; operculum, =269=

_Pythina_, _453_

_Quenstedtia_, _456_

_Quoyia_, 260, _417_

Rachiglossa, 220, _422_; eggs, 124

_Rachis_, 329–335, 441, _442_

_Radiolites_, _456_

_Radius_, _419_

_Radsia_, =403=

Radula, 213 f.; of _Littorina_, =20=; of _Cyclophorus_, =21=; of parasitic Mollusca, 79

_Raëta_, _454_

_Ranella_, 256, _420_

Range of distribution, 362 f.

_Rangia_, 15, _453_

_Ranularia_, _420_

_Rapa_, _423_

_Rapana_, _423_

_Raphaulus_, 305, 309

_Rathouisia_, 316, _440_

Rats devouring Mollusca, 57

_Realia_, 316, 327, _414_

_Recluzia_, _411_

Rectum, 241

_Registoma_, _414_

Relationship of Mollusca to other groups, 5

_Renssoellaria_, 512

Reproductive activity of oyster, 112; system in Mollusca, 123, 134 f.

_Requienia_, 269, =455=, _455_

Respiration, 150 f.

_Retzia_, 508

_Revoilia_, 331, _414_

_Reymondia_, 332

_Rhabdoceras_, _398_

_Rhagada_, 311, 324

_Rhenea_, 325, _440_

_Rhinobolus_, _504_

_Rhiostoma_, 247, =266=, 309, _414_

Rhipidoglossa, 225, _405_

_Rhizochilus_, 75, _423_

_Rhodea_, 356, _441_

_Rhodina_, 307, 310, _442_

_Rhynchonella_, 466, 470, 471, 472, 474, 483, _487_; distribution, 487; fossil, 492, 497, 499, _505_; stratigraphical distribution, 506, 507, 508, 511

Rhynchonellidae, _487_, 501, _505_; stratigraphical distribution, 507, 508, 511

_Rhysota_, 67, 310, 314, 316, 319, _440_

_Rhytida_, 319–326, 333, 359, _440_; habits, 54; radula, =232=

_Rillya_, _442_

_Rimella_, _418_

_Rimula_, 265, _406_

_Ringicula_, _430_; radula, 230

_Risella_, _413_

_Rissoa_, _415_

_Rissoina_, _415_

_Robillardia_, 77

_Rochebrunia_, 331, _414_

Rock-boring snails, 49

_Rolleia_, 349

_Rossia_, _389_

_Rostellaria_, _418_

Rudistae, _456_

_Rumina_, 260, _442_

_Runcina_, _431_; protective coloration, 73

_Sabatia_, _430_

_Sactoceras_, _394_

_Sagda_, =348=-351, _441_

_Sageceras_, _398_

_Salasiella_, 353, _440_

Salivary glands, 237

Sandford, on strength of _Helix_, 45

Sandwich islanders, use of shells, 99

_Sanguinolaria_, _456_

_Sarepta_, _447_

_Sarmaticus_, _409_

_Satsuma_, 314, 316, _441_

_Saxicava_, 447, _457_

_Saxidomus arata_, money made from, 97

_Scalaria_, 247, 263, _411_; radula, 224

_Scaldia_, _452_

_Scalenostoma_, _422_

_Scaliola_, _415_

_Scaphander_, =428=, 429, _430_; radula, =231=; gizzard, =238=

_Scaphites_, =399=, _399_

Scaphopoda, _444_; defined, 6; breathing organs, 160; nervous system, 205; radula, 236

_Scaphula_, =14=, 305, _448_

_Scarabus_, =18=, 278, =439=, _439_

Scharff, R., on food of slugs, 31; on protective coloration in slugs, 70

_Schasicheila_, 347, 351, 354, _410_

_Schismope_, =266=, _407_

_Schizochiton_, 187, 402, _403_

_Schizodus_, _448_

_Schizoglossa_, 325, _440_

_Schizoplax_, _403_

_Schizostoma_, _413_

_Schloenbacia_, _398_

_Scintilla_, 175, _453_

_Scissurella_, 265, _407_; radula, 226

_Sclerochiton_, _403_

_Scrobicularia_, 15, =164=, _453_; siphons, =164=

_Sculptaria_, 333

_Scurria_, _405_

_Scutalus_, 356, _442_

_Scutellastra_, _405_

_Scutus_, 245, =406=, _406_

_Scyllaea_, _433_; jaws, =212=; stomach, 239

_Segmentina_, 320

_Selenites_, 339, 341, _440_

Selenitidae, radula, 231

_Selenochlamys_, 296

Self-fertilisation, 42–44

_Semele_, _453_

_Semicassis_, _420_

Semper, K., on habits of _Limnaea_, 34; of _Helicarion_, 45, 67; on mimicry, 67; on parasitic _Eulima_, 79; on development of _Limnaea_, 84, 94; on sexual maturity in snails, 129; on _Onchidium_, 187

_Sepia_, 381, 385–=387=, _389_; egg-capsules, =127=; glands, 136; jaws, =214=; radula, 236; alimentary canal, =238=; ink-sac, =241=; hectocotylus, =389=

_Sepiadarium_, _389_

_Sepiella_, _389_

_Sepiola_, _389_; glands, 136; radula, 236

_Sepioloidea_, _389_

Sepiophora, _388_

_Sepioteuthis_, _390_; hectocotylus, 139

_Septaria_, 337, 338, _410_

Septibranchiata, 145, 167, _459_; branchiae, =166=

_Septifer_, 274, _449_

_Sequenzia_, _420_

Sergius Orata, 104

_Serrifusus_, _424_

_Sesara_, 305, _440_

Sex, differences of, 133

Shell, 244 f.; internal, 174; shape of bivalve, 445

Shell-gland, primitive, 132

Shells as money, 96 f.; as ornament, etc., 98 f.; various uses of, 98 f.; prices given for rare, 121; sinistral, 249

Shores of N. Asia, no littoral fauna, 2

Showers of shells, 47

_Sigaretus_, =186=, =245=, 267, _411_; foot, =198=

Sight, 180

_Silenia_, _459_; branchiae, 168

_Silia_, _425_

_Siliqua_, 274, _457_

_Siliquaria_, =248=, _418_

_Simnia_, _419_

_Simpulopsis_, 345, 350, _442_

_Simpulum_, _420_

Simroth, on recent forms of _Helix_, 22; on food of slugs, 31; on crawling of _Helix_, 45

Singular habitat, 48

Sinistral shells, 249

_Sinistralia_, _424_

_Sinusigera_, 133

_Sipho_, _424_

_Siphonalia_, _424_

_Siphonaria_, 18, _431_; classification, 19; breathing organs, 151, =152=

Siphonarioidea, _431_

_Siphonodentalium_, _444_

Siphonostomata, 156

_Siphonotreta_, 493, 496, _504_; stratigraphical distribution, 507, 508

Siphons, 173; in burrowing genera, 165; branchial, 155

_Sistrum_, 75, _423_; radula of _S. spectrum_, 79, =222=

_Sitala_, 301, 304, 310, 314–319, 333, _440_

Skärgard, Mollusca of the, 13

_Skenea_, _415_

_Skenidium_, _505_, 508

Slit, in Gasteropoda, 265, 406

Slugs, habits and food of, 30 f.; bite hand of captor, 33; in bee-hives, 36; in greenhouses, 36; protective coloration, 70; eaten in England, 120

_Smaragdia_, 21

_Smaragdinella_, _430_

Smell, sense of, 192

Smith, W. Anderson, quoted, 98, 111, 114, 191

Snails as barometers, 50; plants fertilised by, 102; cultivation for food, 118 f.; used for cream, 119; as medicine, 120; banned by the Church, 121

_Solariella_, _408_; radula, 225

_Solarium_, =264=, _412_, =413=; radula, 224

_Solaropsis_, 343, 353–357, _442_

_Solecurtus_, =165=, _457_

_Solen_, 171, 446, _457_; vision, 190; habits, 45

_Solenaia_, _452_

_Solenomya_, 275, _448_

_Solenotellina_, _456_

Solomon islanders, use of shells, 98

_Somatogyrus_, _415_

_Sophina_, 305

Spallanzani, experiments on _Helix_, 163

Spat, fall of, 113

_Spatha_, 294, 331, 336, _452_

_Spekia_, =333=

Spermatophore, in Cephalopoda, 137; in _Helix_, 142

Spermatozoa, forms of, 136

_Sphaerium_, _453_

_Sphenia_, _456_

_Sphenodiscus_, _398_

_Sphyradium_, _442_

Spines, use of, 64

_Spiraculum_, 266, _414_

_Spiraxis_, _442_

_Spirialis_, 249

_Spirifera_, 468, =501=, _505_; stratigraphical distribution, 507, 508, 511, 512

Spiriferidae, 501, _505_, 508

_Spiriferina_, stratigraphical distribution, 507, 508

Spirobranchiata, 464

_Spirotropis_, _426_; radula, 218, =219=

_Spirula_, 247, 386, _387_, =388=

_Spirulirostra_, 380, 386, _388_

Spondylium, 500

_Spondylus_, 257, 446, =450=, _450_; ocelli, 191; genital orifice, 242

_Spongiobranchaea_, _437_

_Spongiochiton_, _403_

_Sportella_, _453_

Starfish eat oysters, 110

Stearns, R. E. C., on tenacity of life, 38

_Stegodera_, 306

_Stenochisma_, _505_; stratigraphical distribution, 507, 508

_Stenogyra_, 324, _442_; _S. decollata_, 279; food, 34; smell, 194; _Goodallii_, 279; _octona_, sudden appearance, 47

Stenogyridae, radula, 234

_Stenopus_, _440_; habits, 45

_Stenothyra_, _415_

_Stenotis_, _416_

_Stenotrema_, 340, _441_

_Stephanoceras_, _399_

_Stepsanoda_, 358

_Stilifer_, 76, 77, 79, _422_

_Stiliferina_, 76, _422_

_Stiliger_, _432_

_Stilina_, 76

_Stoastoma_, 348–351, _410_

_Stoloteuthis_, _389_

Stomach, 239

_Stomatella_, _408_

_Stomatia_, _408_

_Stomatodon_, 302, _417_

_Strebelia_, 353, _440_

Strength of _Helix_, 45

_Strephobasis_, _417_

_Strepsidura_, _424_

_Streptaulus_, _414_

_Streptaxis_, =302=, 306, 309, 314–331, 343, 357–359, _440_; variation, 87

Streptoneura, 203, 404

_Streptosiphon_, _424_

_Streptostele_, 329, 338, _440_

_Streptostyla_, 343–355, =353=, _440_

_Stricklandia_, _505_; stratigraphical distribution, 507, 508

_Strigatella_, _425_

Stringocephalidae, _506_, 508

_Stringocephalus_, 492, 497, =498=, 500, 501, _506_; stratigraphical distribution, 507, 508

_Strobila_, 340, 345–353

_Strobilops_, _442_

Strombidae, habits, 64; penis, 136

_Strombina_, _423_

_Strombus_, =69=, =200=, 252, _418_; mimicking _Conus_, 69; operculum, =78=, =269=; pearls from, 101; metapodium, 199; stomach, 239

_Strophalosia_, _504_; stratigraphical distribution, 507, 508

_Stropheodonta_, 497, _505_, 508

_Strophia_, 343–355, _442_; _S. nana_, 278

_Strophochilus_, 358, _441_

_Strophomena_, 499, _505_; stratigraphical distribution, 507, 508

Strophomenidae, 500, _505_, 508

_Strophostoma_, 248, _414_

Structure of shell, 252

_Struthiolaria_, 99, _418_; radula, 216

_Styliola_, _437_

_Stylodonta_, 339, _441_

Stylommatophora, 11, 181, _439_; origin, 19

_Subemarginula_, _406_

Submytilacea, _451_

_Subularia_, _422_

_Subulina_, 332, 352, _442_

_Subulites_, _420_

_Succinea_, 325, 327, 358, _433_; jaw, =211=; _S. putris_, parasite of, 61

Succineidae, _443_; radula, 234

Sudden appearance of Mollusca, 46

_Suessia_, stratigraphical distribution, 507

Sulphuric acid, 237

_Surcula_, _426_

_Sycotypus_, _424_

_Synaptocochlea_, _408_

_Syndosmya_, _453_

_Syringothyris_, 500, 508

_Syrnola_, _422_

_Syrnolopis_, 332, =333=

_Systrophia_, 356, 357

_Tachea_, _441_

Taenioglossa, 223, _411_

_Taheitia_, _414_

_Talona_, _457_

_Tanalia_, 304, _417_

_Tancredia_, _453_

_Tanganyicia_, 332, _415_

Tanganyika, L., fauna of, 12

_Tanysiphon_, _454_

_Taonius_, =391=, _391_

_Tapes_, _454_

Taste, 179

_Tebennophorus_, 143, 340, _440_

_Tectarius_, _413_

Tectibranchiata, 10, _429_

_Tectura_, 305, _405_

_Tectus_, _408_

Teeth in aperture of the shell, 63

_Teinostoma_, 247, _408_

_Teinotis_, _407_

_Telescopium_, 252, _416_

_Tellina_, 440, =453=, _453_; _T. balthica_, variation, 84

Tellinacea, _453_

Telotremata, 511

Tenacity of life, 37

Tenison-Woods, on red blood, 171; on shell-eyes, 189

Tennent, Sir J. E., on musical sounds produced by Mollusca, 50

_Tennentia_, 304, 314, 338, _440_

_Terebellum_, _418_; jumping powers, 64

_Terebra_, =246=, 263, =426=, _426_; radula, =219=

_Terebratella_, 468, _487_; distribution, 486; fossil, _506_; stratigraphical distribution, 508

_Terebratula_, 467, 468, _487_; size, 484; distribution, 485, 486; fossil, 492, =499=, _506_; stratigraphical distribution, 506, 507, 508

Terebratulidae, _487_; fossil, 500, _505_, _506_; stratigraphical distribution, 507, 508

_Terebratulina_, =466=, 479, _487_; larva, =482=; distribution, 486; fossil, _506_; stratigraphical distribution, 508; form of shell, 510

_Teredina_, _457_

_Teredo_, 262, =457=, _458_; nervous system, =206=; intestine, =241=

_Tergipes_, _432_

_Terquemia_, _450_

_Testacella_, 22, =52=, _440_; habits, etc., 49, 51 f.; pulmonary orifice, 160; eyes, 186; radula, 231; anus, 241

Testicardines, 466, _487_; muscles, 476; fossil, 497, _504_; external characters, 497; internal characters, 499; attachment of muscles, 501; stratigraphical distribution, 508

Testis, 135

Tethyidae, 216

_Tethys_, _432_

Tetrabranchiata, _391_ f.

_Thala_, _425_

_Thalassia_, 319

_Thalotia_, _408_

_Thapsia_, 329

_Thaumasia_, 349, _442_

_Thaumastus_, 356, _442_

_Thecacera_, _434_; radula, 229

Thecidiidae, _487_; fossil, 501, _506_, 508

_Thecidium_, 475, 479, =480=, 483, _487_; fossil, _506_, 508

Thecosomata, _435_

_Thelidomus_, 346–351, =350=, _441_

_Theora_, _453_

_Therasia_, _441_

_Thersites_ (Helicidae), 322, 325

_Thersites_ (Fasciolariidae), _424_

_Thetis_, _454_

_Thracia_, 245, _459_

Thread-spinning, 29

_Thridachia_, _432_

_Thyca_, 76, 79

_Thyrophorella_, 330, _440_

_Thysanoteuthis_, _390_

_Tiedemannia_, veliger, =132=

_Tiphobia_, 332, =333=, _417_

Titicaca, L., Mollusca of, 25

_Todarodes_, _390_

_Tomichia_, _414_

_Tomigerus_, 334, 356, 358, _442_

_Tomocyclus_, 354

_Tomostele_, 330, _440_

_Tonicella_, _403_

_Tonicia_, _403_; eyes, 188

_Torellia_, _411_

_Torinia_, _413_; radula, 224; operculum, =269=

_Tornatellina_, 278, 319, 323–327, 338, 358, _443_

_Tornatina_, 250, _430_

_Torquilla_, _442_

_Toucasia_, _455_

Touch, sense of, 177

Toxoglossa, 218, _426_

_Trachia_, 314

_Trachyceras_, _397_

_Trachydermon_, _403_

_Trachyteuthis_, _389_

_Tralia_, _439_

_Transovula_, _419_

_Trematis_, 492, 493, _504_; stratigraphical distribution, 507, 508

_Trematonotus_, _407_

_Tremoctopus_, _384_; radula, 236; hectocotylus, 137

_Trevelyana_, _434_

_Trichia_, 316

_Trichotropis_, 275, _411_

_Tricula_, 302

_Tridacna_, =273=, _455_

_Triforis_, _416_; radula, 224

_Trigonellites_, =397=

_Trigonia_, =15=, 254, 269, _448_; jumping powers, 65; distribution, 370

_Trigonochlamys_, 296, _440_

_Trigonostoma_, _426_

_Trimerella_, =495=, _504_, 508, 511

Trimerellidae, 493, 494, 496, _504_; stratigraphical distribution, 507, 508

_Trinacria_, _448_

_Triodopsis_, 340, _441_

_Triopa_, _434_

_Triopella_, _434_

_Triopha_, _434_

_Tritaxeopus_, _385_

_Triton_, 256, =275=, _420_; jaws, =212=

_Tritonia_, _433_; protective coloration, 71

_Tritonidea_, _424_

_Trivia_, _419_

Trochidae, egg-capsules, 125

_Trochiscus_, _408_

_Trochita_, 248, _412_

_Trochoceras_, _395_

_Trocholites_, _395_

_Trochomorpha_, 306, 321, 324, 327, 333, _441_

_Trochonanina_, 331, _440_

Trochosphere, 5, 130

_Trochotoma_, 266, _407_

_Trochus_, 263, _408_; eye, 182; stomach, 239

_Trophon_, _423_

Tropical beach, Mollusca of a, 3

_Tropidophora_, _414_

_Tropites_, _397_

_Troschelia_, _424_

_Truncaria_, _423_

_Truncatella_, 260, _414_

_Tryblidium_, _405_

_Trypanostoma_, 340

Trypho of Lampsacus, prayer against snails, 121

Tubed operculates, 157, 266, 300, 307, 309

_Tudicla_, _424_

_Tudora_, 291, 349, 351, _414_

_Tugonia_, _456_

_Tulotoma_, 340, _416_

_Turbinella_, 100, 262, =264=, =424=, _424_

_Turbo_, _409_; eye, =182=; osphradium, 195; operculum, =268=

_Turbonilla_, 250, 332, _422_

_Turcica_, _408_

_Turricula_, _425_; radula, 221

_Turrilites_, =399=, _399_

_Turritella_, 252, _417_; radula, 215, 224

_Tyleria_, _459_

_Tylodina_, _431_

_Tylopoma_, _416_

_Tympanotonus_, _416_

_Tyndaria_, _447_

_Typhis_, _423_

Ultra-dextral shells, 250

_Umbonella_, _409_

_Umbonium_, _409_

_Umbrella_, =10=, _431_; radula, 217, 230

_Uncites_, _505_; stratigraphical distribution, 507, 508

Underground snails, 48

_Ungulina_, _452_

_Unicardium_, _452_

_Unio_, _452_; shell, =254=, 259, =273=, 341; variation, 92

Union of _Limax_, 128

Unionidae, origin of, 15; eaten by rats, 57; larvae, 146

_Urocyclus_, =331=, _440_

_Urosalpinx_, _423_

_Utriculus_, _430_

_Uvanilla_, _409_

_Vaginula_, 245, 319, 343, 352, _443_

Vaginulidae, radula, 234; anus, 241

_Valletia_, _456_

_Vallonia_, _441_

_Valvata_, 133, _416_; branchia, =159=

Valves of Chitonidae, 401 f.

_Vanganella_, _454_

Variation, 82 f.

_Varicella_, 346, 348

_Velates_, 260, _410_

_Velifera_, 353, _440_

Veliger stage, 131; mistaken for perfect form, 133

_Velorita_, 302, _453_

Velum, 131

_Velutina_, 275, _411_; radula, 223

Veneracea, _454_

_Venericardia_, _451_

_Venerupis_, _454_

_Veniella_, _451_

_Venilicardia_, _451_

_Venus_, =270=, =271=, 446, _454_; _V. mercenaria_, 97, 374

_Verania_, _391_

_Vermetus_, 247, _418_; radula, =223=

_Veronicella_, _443_

_Verticordia_, _458_

_Vertigo_, 327, _442_; _V. arctica_, 287

_Vexilla_, _423_

_Vibex_, _417_

_Vitrella_, 289

_Vitrina_, 22, 296 f., 332, _440_; hardy habits, 24; jumping powers, 65; shell, 175; radula, 217

_Vitrinella_, _408_

_Vitriniconus_, 314, _440_

_Vitrinoidea_, 314, _440_

_Vitrinozonites_, 340, _440_

_Vitularia_, _423_

_Vivipara_, 324, 343, _416_

Volume of water, effect in producing variation, 94

_Voluta_, 267, =425=, _425_; spawn, =125=; radula, 217, 221; distribution, 370; prices given for rare, 122

_Volutaxis_, 348

_Volutharpa_, 267, _424_

_Volutolithes_, _425_

_Volutolyria_, _425_; radula, 222

_Volutomitra_, _425_; radula, 221

_Volutopsis_, _423_

_Volvaria_, _429_

_Volvatella_, _430_

_Volvula_, _430_

_Vulsella_, 75, =446=, _449_

_Waldheimia_, 464, 467, 468, 473, 474, _487_; size, 484; distribution, 486; fossil, =500=, 501, 502, _506_, 508

Walton and mussel cultivation, 115

Wampum, 97

Warner, R., quoted, 37

Warning coloration, 71 f.

West Coast, South America, melanism of shells occurring on, 85

Whelks, use of, 118

_Whitneya_, _424_

Whitstable, oyster-parks at, 106, 112

Willem, V., on vision of Mollusca, 185

Wollaston, T. V., quoted, 32

Wood, Rev. J. G., on starfish eating oysters, 111

_Woodia_, _451_

Woodward, S. P., on tenacity of life, 38; Dr., on the same, 38

Wotton, F. W., on egg-laying of _Arion_, 42

Wright, Bryce, on tenacity of life, 38

_Xenophora_, _412_; habits, =64=

_Xenopoma_, 346, 351

_Xerophila_, 285, 296, _441_

_Xesta_, 310, 319, 321, _440_; mimicry by, 66 f.

_Xylophaga_, _457_

_Yetus_, _425_

_Yoldia_, _447_; genital orifice, 242

_Zagrabica_, 297

_Zebrina_, 285, 296, _442_

_Zeidora_, _406_

_Zidona_, _425_

_Zittelia_, _420_

Zones of depth, 361

_Zonites_, 275, _440_; food, 33; radula, 232; distribution, 294, 296, 340

_Zospeum_, 187, _442_

Zygobranchiata, 154, _406_

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FOOTNOTES:

[1] See especially Moseley, _Nature_, 1885, p. 417.

[2] _Quart. Journ. Conch._ i. p. 371.

[3] _Manuel de Conchyliologie et de Paléontologie Conchyliologique._ Dr. P. Fischer. Paris, 1887.

[4] κεφαλή, head; γαστήρ, stomach; σκάπτειν, to dig; πέλεκυς, an axe; πούς, ποδός, a foot.

[5] Also known as _Lamellibranchiata_, _Conchifera_, and _Acephala_.

[6] πτερόν, wing.

[7] γλῶσσα, tongue; φέρειν, to carry.

[8] λείπειν, to be wanting.

[9] ἀμφί, on both sides; νεὕρον, nerve, vessel. Some authorities regard the Amphineura as a distinct Order.

[10] πολύς, many; πλάξ, plate.

[11] πρόσω, in front. Often alluded to in the sequel as ‘operculate Gasteropoda.’

[12] κτενίδιον, a little comb.

[13] δὐω, two; mόnos, single; ὦτα, auricles; καρδία, heart.

[14] ὄπισθεν, behind.

[15] _Pulmo_, a lung.

[16] στὕλος, pillar; ὄμματα, eyes.

[17] The _Ascoglossa_ are dealt with below (chap. xv.).

[18] Beudant, by very gradually changing the water, accustomed marine species to live in fresh, and fresh-water species to live in salt water.

[19] Braun, _Arch. f. Naturk. Liv._ (2), x. p. 102 f.

[20] Lindström, _Oef. K. Vet. Förh. Stockh._, 1855, p. 49.

[21] Mendthal, _Schr. Ges. Königsb._, xxx. p. 27.

[22] _SB. K. Akad. Wiss. Wien_, 1889, p. 4, but the view is not universally accepted.

[23] Not to _Nassa_, as has been generally held. The shape of the operculum, and particularly the teeth of the radula, show a much closer connexion with _Cominella_.

[24] _E.g._ Bouvier, _Le Natural_, 1889, p. 242.

[25] Köhler, _Zool. Jahrb._ vii. 1893, p. 1 f; Haller, _Arb. Zool. Inst. Wien_, x. p. 71.

[26] Plate, _SB. kön. Preuss. Ak. Wiss. Berl._ 1893. p. 959.

[27] _E.g._ Pelseneer, _Bull. Sc. France Belg._ xxiv. p. 347 f.

[28] _E.g._ Bergh, _Zool. Jahrb._ v. p. 1 f.

[29] Calkins, _Amer. Nat._ xi. p. 687.

[30] One step even further (or perhaps it should be termed a branch derivative) is seen in the genus _Smaragdia_, which is probably a _Neritina_ which has resumed a purely marine habit of life.

[31] _SB. Naturf. Gesell. Leipz._ 1886–87, pp. 40–48.

[32] _L. and F. W. Moll. of India_, iv. p. 167.

[33] T. Scott, _Journ. of Conch._ v. p. 230.

[34] J. S. Gibbons, _ibid._ ii. p. 129.

[35] _Bull. Soc. Linn. Nord_, Abbeville, 1840, p. 150.

[36] Joly, _Comptes Rendus_, 1842, p. 460; compare W. A. Gain, _Science Gossip_, xxvii. p. 118.

[37] Von Martens, _SB. Nat. Fr. Berl._ 1881, p. 34.

[38] Moquin-Tandon, _Moll. de France_, i. p. 116.

[39] _Journ. of Conch._ iii. p. 321 f.; iv. p. 13; _Science Goss._ 1866, p. 158.

[40] Reichel, _Zool. Anz._ x. p. 488.

[41] Schumann, _Schr. Ges. Danz._ (2) vi. p. 159.

[42] Fischer and Crosse, _Mexico_, p. 437.

[43] _Journ. de Conch._ iv. p. 397, but the species observed is not mentioned.

[44] _Bull. Mus. C. Z. Harv._ iv. p. 378.

[45] W. Harte, _Proc. Dubl. N. H. Soc._ iv. p. 182.

[46] See on the whole subject of threads G. S. Tye, _Journ. of Conch._ i. p. 401.

[47] _Zoologist_, ii. p. 296; iii. p. 833; iv. p. 1216; iii. p. 1036; iv. p. 1216; iii. p. 1037.

[48] _Ann. Nat. Hist._ ii. 1838, p. 310.

[49] H. W. Kew, _Naturalist_, 1889, p. 103.

[50] _Zeit. wiss. Zool._ xlii. p. 203 f.

[51] _Sci. Trans. R. Dubl. Soc._ (2) iv. p. 520.

[52] _Zoologist_, iv. p. 1504; iii. p. 1038; iii. p. 943.

[53] H. W. Kew, _l. c._

[54] _Zoologist_, xix. p. 7819.

[55] _Naturalist_, 1889, p. 55.

[56] H. W. Kew, _l. c._

[57] W. G. Binney, _Bull. Mus. C. Z. Harv_. iv. p. 144.

[58] _Naturalist_, _l. c._

[59] _Science Gossip_, 1885, p. 154.

[60] R. Standen, _Journ. of Conch._ vii. p. 197.

[61] _Journ. of Conch._ v. p. 43.

[62] A. Paladilhe in MS. letter.

[63] J. S. Gibbons, _Quart. Journ. Conch._ ii. p. 143.

[64] _Bull. Mus. C. Z. Harv._ iv. p. 193.

[65] _l. c._ p. 362.

[66] _Animal Life_, p. 59.

[67] _Zoologist_, 1861, p. 7400; _Brit. Conch._ i. p. 108.

[68] H. Ullyett, _Science Gossip_, xxii. (1886), p. 214.

[69] _Descent of Man_, i. p. 325, ed. 1.

[70] _Amer. Nat._ xv. 1881, p. 976.

[71] W. A. Gain, quoted by H. W. Kew in _Naturalist_, 1890, p. 307, an article to which I am much indebted.

[72] _Ann. Mag. Nat. Hist._ (5) xvi. p. 519.

[73] _Science Gossip_, 1882, pp. 237, 262.

[74] H. W. Kew, _Naturalist_, 1893, p. 149, another most valuable article.

[75] _Garden_, v. p. 201, quoted by Kew, _ut sup._

[76] Kew, _ut sup._

[77] _Science Gossip_, 1883, p. 163.

[78] T. D. A. Cockerell, _Science Gossip_, 1885, p. 211.

[79] _Ann. Mag. Nat. Hist._ (2) vi. (1850) p. 68.

[80] _Ann. Mag. Nat. Hist._ (2) vi. p. 489.

[81] _Ibid._ (3) iii. p. 448.

[82] _Amer. Nat._ xi. (1877) p. 100; _Proc. Calif. Ac._ iii. p. 329.

[83] _Gaz. Med. Alger._ 1865, 5th Jan. p. 9.

[84] _Science Gossip_, 1867, p. 40.

[85] _Ann. Mag. Nat. Hist._ (2) ix. p. 498.

[86] _Journ. of Conch._ vi. p. 101.

[87] _Naturalist_, 1889, p. 55.

[88] _Malak. Blätt._ (2) iv. pp. 43 and 221.

[89] _Phil. Trans._ 1854 (1856), p. 8.

[90] _Naturalist_, 1891, p. 75 f.; _Conchologist_, ii. 1892, p. 29.

[91] Taylor, _Journ. of Conch._ 1888, p. 299.

[92] See Tennent’s _Ceylon_, i. p. 221, ed. 5.

[93] W. A. Gain, _Naturalist_, 1889, p. 55; Brockmeier, _Nachr. Deutsch. Malak. Gesell._ xx. p. 113.

[94] _Ann. Mag. Nat. Hist._ (2) ix. p. 498.

[95] _Journ. Conch._ vii. 1893, p. 158 f.

[96] I succeeded in hatching out eggs of _Helix aspersa_, during the very warm summer of 1893, in 17 days.

[97] _Nachr. Deutsch. Malak. Gesell._ xx. p. 146.

[98] Raymond, _Nautilus_, iv. p. 6.

[99] Quoted by Oehlert, _Rév. Sc._ xxxviii. p. 701.

[100] _Animal Life, Intern. Scientif. Ser._ ed. 1, p. 395.

[101] _Zoologist_, 1886, p. 491.

[102] Thomas, quoted by Jeffreys, _Brit. Conch._ i. p. 30.

[103] _Journ. of Conch._ iv. p. 117.

[104] Rev. L. Jenyns, _Observations in Nat. Hist._ p. 318.

[105] _Id. ib._ p. 319.

[106] Further detailed examples will be found in Kew, _The dispersal of Shells_, pp. 5–26.

[107] _P. Z. S._ 1888, p. 358.

[108] W. A. Gain, _Naturalist_, 1889, p. 58.

[109] _Das Wetter_, Dec. 1892. Another case is recorded in _Amer. Nat._ iii. p. 556.

[110] _Zoologist_, x. p. 3430.

[111] _Science Gossip_, 1888, p. 281.

[112] Lecoq, _Journ. de Conch._ ii. p. 146.

[113] Bouchard-Chantereaux, _Ann. Sci. Nat. Zool._ (4) xvi. (1861) p. 197.

[114] Forel, _Ann. Sci. Nat._ (3) xx. p. 576; Bretonnière, _Comptes Rendus_, cvii. p. 566.

[115] Brit. Mus. Collection.

[116] Thomas, quoted by Récluz in _Journ. de Conch._ vii. 1858, p. 178.

[117] _Nat. Hist. of Ceylon_, p. 382. See also T. L. Taylor, _Rep. Brit. Ass._ for 1848, p. 82.

[118] Dr. R. E. Grant, _Edinb. Phil. Journ._ xiv. p. 188.

[119] _Rep. Brit. Ass._ for 1848, p. 80. The statement is confirmed by Rossmässler.

[120] _Journ. of Conch._ iv. p. 118.

[121] _Zoologist_, 1887, p. 29.

[122] _Arch. Zool. Exp. Gén._ (2) v. p. 459 f.

[123] _Journ. of Conch._ iii. p. 277; compare W. M. Webb, _Zoologist_, 1893, p. 281.

[124] _Bull. Mus. Comp. Zool. Harv._ iv. p. 85.

[125] Erjavec, _Nachr. Deutsch. Malak. Gesell._ 1885, p. 88.

[126] Crosse, _Journ. de Conch._ (3) xiv. (1874) p. 223.

[127] C. Wright, _Zoologist_, 1869, p. 1700.

[128] W. V. Legge, _Zoologist_, 1866, p. 190.

[129] Blackwall, _Researches_, p. 139.

[130] Barrow, _Travels in South Africa_, ii. p. 67.

[131] _Loch Creran_, p. 102.

[132] Cordeaux, _Zoologist_, 1873, p. 3396.

[133] _Amer. Nat._ xii. p. 695; _Science Gossip_, 1865, p. 79.

[134] _Journ. Trent. N. H. Soc._ 1887, p. 58.

[135] _Ann. Nat. Hist._ iii. 1893, pp. 238, 239.

[136] _Rev. Nat. Sc. Ouest_, 1891, p. 261.

[137] Petit de la Saussaye, _Journ. de Conch._ iii. p. 97 f.

[138] J. W. Williams, _Science Gossip_, 1889, p. 280.

[139] Noack, _Zool. JB._ ii. p. 254.

[140] _La Nature_, xv. (2) p. 46.

[141] François, _Arch. Zool. Exp. Gén._ (2) ix. p. 240.

[142] A. Lang, _Ber. Naturf. Ges. Freib._ vi. 1892, p. 81.

[143] A. P. Thomas, _Q. J. Micr. Sc._ N. S. xxiii. (1883) p. 99.

[144] H. Woodward, _P. Z. S._ 1886, p. 176.

[145] W. E. Collinge, _Zoologist_, 1890, p. 467.

[146] _Proc. Linn. Soc. N. S. Wales_, ix. p. 944.

[147] _Zoologist_, xviii. (1860) p. 7136.

[148] A. Adams, _Samarang_, vol. ii. _Zoology_, p. 357.

[149] In Thomson’s _British New Guinea_, p. 283.

[150] _Animal Life_, p. 395. It should be mentioned that Von Möllendorff (_Ber. Senck. Ges._ 1890, p. 198) ridicules the whole theory.

[151] Von Martens, _SB. Nat. Fr. Berl._ 1891, p. 83.

[152] Von Martens, _ibid._ 1887, p. 183.

[153] _SB. Nat. Gesell. Leipz._ xiii.-xiv. p. 45.

[154] Garstang, _Journ. Mar. Biol. Ass._ N. S. i. p. 432; Giard, _Bull. Sci. Fr. Belg._ 1888, p. 502 f.

[155] _Nautilus_, vi. 1892, p. 90.

[156] R. F. Scharff, _Sci. Trans. R. Dubl. Soc._ (2) iv. p. 553 f.

[157] _Q. Journ. Micr. Sci._ N. S. xxxi. (1890) p. 41 f.

[158] A detailed account is given in _Proc. Liverp. Biol. Soc._ iv. (1890) pp. 150–163.

[159] _Journ. Mar. Biol. Ass._ N. S. i. p. 418 f.

[160] Garstang, _Conchologist_, ii. p. 49.

[161] Hecht, _Comptes Rendus_, cxv. p. 746.

[162] _Conchologist_, ii. p. 130.

[163] Described as a _Cypraea_, but no doubt an _Ovula_ or _Pedicularia_: _CB. Bakt. Par._ v. p. 543.

[164] Von Graff, _Z. wiss. Zool_ xxv. p. 124.

[165] _Proc. Amer. Phil. Soc._ xxv. p. 231.

[166] _Ergeb. naturw. Forsch. Ceylon_, abstr. in _Journ. Roy. Micr. Soc._ (2) vi. p. 412.

[167] _Voyage of the Samarang_, Moll. p. 69, Pl. xi. f. 1; p. 47, Pl. xvii. f. 5.

[168] E. A. Smith, _Ann. Mag. Nat. Hist._ (6) iii. p. 270.

[169] _Journ. de Conch._ (3) xxix. p. 101.

[170] _Zool. Jahrb. Abth. f. Syst._ v. p. 619.

[171] See especially Semper, _Animal Life_, Ed. 1, p. 351.

[172] Gould, _Moll. of U.S. expl. exped._ 1852, p. 207 (_St. acicula_, from Fiji).

[173] Stimpson, _Proc. Bost. Soc. N. H._ vi. 1858, p. 308.

[174] Pidgeon, _Nature_, xxxix. p. 127.

[175] W. Anderson Smith, _Loch Creran_, p. 46.

[176] Smart, _Journal of Conch._ v. p. 152.

[177] _Animal Life_, p. 351.

[178] _Journ. of Conch._ vi. 1891, p. 399.

[179] _Ann. Mag. N. H._ (6) vii. p. 276.

[180] Stimpson, quoted by Jeffrey’s _Brit. Conch._ ii. 194.

[181] Stimpson, _Journ. Bost. Soc. N. H._ vi. 1857, p. 48.

[182] E. H. Matthews, _Conchologist_, ii. p. 144.

[183] Thus _Limnaea involuta_, which is almost universally regarded as a good and distinct species, has been held to be no more than a variety of _L. peregra_ produced by locality; see _Zoologist_, 1889, p. 154.

[184] J. W. Taylor, _Journ. of Conch._ v. p. 289, an interesting article, with many useful references.

[185] Möbius, _Report on ‘Pommerania’ Exped._ pp. 138–141.

[186] _Journ. de Conchyl._ xxiii. 1875, p. 105.

[187] J. W. Taylor _ut sup._ p. 300.

[188] _Sci. Trans. R. Dubl. Soc._ (2) iv. p. 555.

[189] J. S. Gibbons, _Journ. of Conch._ ii. p. 129.

[190] C. H. Morris, _ibid._ vii. p. 191.

[191] F. M. Hele, _ibid._ iv. p. 93.

[192] T. D. A. Cockerell, _Science Gossip_, 1887, p. 67.

[193] J. G. Jeffreys, _British Conchology_, vol. i. p. 214.

[194] _Journ. of Conch._ vi. p. 123.

[195] _Phil. Trans._ 1889, vol. 180 B, p. 207. A somewhat similar case (the celebrated Steinheim series of _Planorbis_) is dealt with by Hilgendorf, _MB. Akad. Berl._ 1866, p. 474; and Hyatt, _Proc. Amer. Ass. Sc._ xxix. p. 527.

[196] J. B. Bridgman, _Quart. Journ. Conch._ i. p. 70.

[197] W. C. Hey, _Journ. of Conch._ iii. p. 268.

[198] _Zool. Anz._ xiii. p. 662.

[199] J. Madison, _Journ. of Conch._ v. p. 260.

[200] _Quart. Journ. Conch._ i. 339.

[201] Whitfield, _Bull. Amer. Mus. N. H._ i. p. 29.

[202] _Amer. Nat._ xiv. p. 51.

[203] _Animal Life_, Ed. 1, p. 160 f.

[204] _Conch. Syst._ ii. p. 262 _n._

[205] P. L. Simmonds, _Commercial Products of the Sea_, p. 278.

[206] _Benderloch_, p. 118.

[207] C. Hedley in J. P. Thomson, _Brit. New Guinea_, p. 283.

[208] Most of the above facts are derived from a study of a collection of native implements, weapons, ornaments, etc., in the Antiquarian Museum at Cambridge.

[209] Thurston, _Notes on the Pearl and Chank Fisheries_, Madras, 1890.

[210] See in particular, P. L. Simmonds, _The Commercial Products of the Sea_.

[211] H. Friend, _Field Club_, iv. 1893, p. 100.

[212] _Nature_, xxxi. 1885, p. 492.

[213] W. Anderson Smith, _Benderloch_, p. 173.

[214] Dominique, _Feuill. Nat._ xviii. p. 22.

[215] SB. _Nat. Fr. Berl._ 1889, p. 197.

[216] A. Adams, _Voyage of the ‘Samarang,’_ ii. p. 308.

[217] Much information has been derived, on this subject, from Bertram’s _Harvest of the Sea_, Simmonds’ _Commercial Products of the Sea_, the publications of the Fisheries Exhibition, especially vol. xi. (Anson and Willett); see also Philpots, _Oysters and all about them_.

[218] Juvenal, _Sat._ iv. 140–142.

[219] _Hist. Nat._ ix. 79.

[220] _Vol. Max._ ix. 1.

[221] _Quart. Journ. Micr. Sc._ xxvi. p. 71.

[222] See G. H. Lewes, _Sea-side Studies_, p. 339.

[223] _Bull. U.S. Fish. Comm._ v. p. 161.

[224] W. Anderson Smith, _Loch Creran_, p. 228.

[225] _Longmans’ Magazine_, June 1889.

[226] _St. James’s Gazette_, 6th January 1893.

[227] Also at Arcachon (W. A. Herdman, _Nature_, 1893, p. 269).

[228] See especially Hoek, _Tijdschr. Ned. Dierk. Vereen_, Suppl. Deel, i. 1883.

[229] _Benderloch_, p. 136.

[230] This is the view of E. Ray Lankester, _Quart. Journ. Micr. Sc._ xxvi. 80.

[231] De Quatrefages, _Rambles of a Naturalist_.

[232] Quoted by Jeffreys, _Brit. Conch._, ii. p. 109.

[233] M. S. Lovell, _Edible Mollusks_, p. 49.

[234] _Science_, vii. p. 175.

[235] _Hist. Nat._ ix. 82.

[236] _De re rustica_, iii. 14.

[237] _Epistles_, i. 15.

[238] Hor. _Sat._ II., iv. 58, tr. Conington.

[239] Roberts, _Zoologist_, 1885, p. 425.

[240] _Hist. Nat._ xxx. 15, 19.

[241] _Science Gossip_, 1891, p. 166.

[242] Jeffreys, _Brit. Conch._ iii. p. 355.

[243] W. Clark, _Mag. Nat. Hist._ xvi. p. 466.

[244] Examples will be found in _Journ. Linn. Soc. Zool._ xi. p. 90; _Ann. Sc. Nat._ xx. p. 472; _Zeit. wiss. Zool._ xxiv. p. 419.

[245] Herdman, _Proc. Liverp. Biol. Soc._ iii. p. 30.

[246] Garrett, _Journ. Ac. Nat. Sc. Phil._ viii. (1880).

[247] J. Bladon, _Zoologist_, xvi. p. 6272.

[248] Lo Bianco, _MT. Zool. Stat. Neap._ viii. p. 414.

[249] _Animal Life_, pp. 126, 135.

[250] R. Rimmer, _Land and Fresh-Water Shells_, p. 119.

[251] _Journ. de Conch._ ii. p. 245.

[252] _Journ. de Conchyl._ iii. p. 107.

[253] Jeffreys, _Brit. Conch._ iii. p. 359; Sauvage, _Journ. de Conchyl._ xxi. p. 122.

[254] Hermaphroditism seems to occur in (_a_) whole families, _e.g._ _Anatinidae_ and the _Septibranchia_; (_b_) genera, _e.g._ _Cyclas_, _Pisidium_; (_c_) single species, _e.g._ in the generally dioecious genera _Ostrea_, _Pecten_, _Cardium_.

[255] δὐω, two; μόνος, single; γόνος, semen; πόρος, passage.

[256] Von Brunn, _Arch. Mikr. Anat._ xxiii. p. 413.

[257] _Hist. Anim._ v. 6 and 12, iv. 1, ed. Bekker, 1837.

[258] ‘On pourra constater si ce ne seraient pas des parties détachées de quelque céphalopode dans le but de servir à le fécondation,’ _Hist. Nat. Helminthes_, 1845, p. 482.

[259] Steenstrup, _Ann. Mag. Nat. Hist._ (2), xx. p. 81 f.

[260] C. Ashford, _Journ. of Conch._ iii. p. 239, iv. pp. 69, 108.

[261] W. E. Collinge, _Zoologist_, 1890, p. 276.

[262] Pelseneer, _Comptes Rendus_, cx. p. 1081.

[263] _Kon. Vet. Akad. Handl._ 1848, pp. 329–435.

[264] _P. Z. S._ 1891, p. 52 f.

[265] The result of some experiments by Professor Herdman upon _Littorina rudis_, tends to show that it can live much better in air than in water, and goes far to support the view that the species may be undergoing, as we know many species must have undergone (see p. 20), a transition from a marine to a terrestrial life. It was found that marked specimens upon the rocks did not move their position for thirty-one successive days (_Proc. Liverp. Biol. Soc._ iv. 1890, p. 50).

[266] Diminutive of κτείς, a comb.

[267] Stoliezka, quoted in _Journ. de Conch._ xviii. p. 452.

[268] ζύγος, a yoke, from the symmetrical position of the branchiae.

[269] Pelseneer, _‘Challenger’ Reports_, vol. xxiii. part lxvi.

[270] _Zoologist_, xii. p. 4248.

[271] _Mollusques de France_, i. p. 81.

[272] _N. Denk. Schw. Ges._ xxix. (2) p. 196 f.

[273] Bergh, _Morph. Jahrb._ x. p. 172.

[274] P. Fischer, _Journ. de Conch._ ix. p. 101.

[275] _Bull. Mus. C. Z. Harv._ xviii. p. 434.

[276] Pelseneer, _Comptes Rendus_, cvi. p. 1029.

[277] _E.g._ Kollmann, _Zeit. wiss. Zool._ xxvi. p. 87.

[278] _Proc. Roy. Soc._ 1873, p. 70.

[279] Griesbach (_Arch. mikr. Anat._ xxxvii. p. 22) finds haemoglobin in several bivalves, _e.g._ _Poromya granulata_, _Tellinata planata_, _Arca Noae_, and _Pectunculus glycimeris_.

[280] _Trans. Roy. Soc. N. S. Wales_, xxii. p. 106.

[281] Pelseneer, _Comptes Rendus_, cx. p. 154.

[282] _Science_, iv. p. 50.

[283] P. Fischer, _Journ. de Conchyl._ (3) xxvii. p. 201.

[284] _Journ. of Conch._ vi. p. 349 ff.

[285] _Quart. Journ. Micr. Sc._ N.S. xv. p. 37.

[286] _Ann. Mag. Nat. Hist._ (2), xx. p. 336.

[287] V. Willem (_Arch. Biol._ ut infr.) denies this, and declares that _Cyclostoma_ is only very sensitive to movements. The present writer has often approached, with the greatest care, a crawling _Cyclostoma_, but it always withdrew into its shell or fell to the ground when approached within about 10 or 12 inches.

[288] _Arch. Biol._ xii. 1892, p. 57.

[289] _‘Challenger’ Reports_, Zoology, vol. xxvii. part lxxiv. p. 3.

[290] _Animal Life_, p. 372 f.

[291] Bergh, _Morph. Jahrb._ x. p. 172.

[292] _Ann. Mag. Nat. Hist._ (5) xiv. p. 141.

[293] The nature of the grouping of the eyes into rows varies considerably in different species. As a rule, the rows radiate from the beak, but occasionally they run parallel to the girdle. In _Tonicia lineolata_ Fremb., they are grouped, as it were, under the shelter of strongly marked longitudinal wavy lines.

[294] =Shell-Eyes in other Mollusca.=--The Rev. J. E. Tenison-Woods (_Trans. Linn. Soc. N. S. Wales_, xxii. p. 106) is of opinion that ‘shell-eyes’ are by no means confined to the Chitonidae, but that, in fact, multiplicity of eyes of this kind is the rule rather than the exception among the Mollusca. He finds (1) exceedingly minute and numerous ‘eyes’ on the outer surface of the shell in both univalves and bivalves; (2) large and solitary ‘eyes’ in the shell substance; (3) eyes on the mantle lobes in both univalves and bivalves; (4) eyes on the opercula.

[295] _Mitth. Stat. Zool. Neap._ v. p. 447 ff.

[296] W. Patten, _Mitth. Zool. Stat. Neap._ vi. (1886) pp. 546, 605 f.

[297] _Benderloch_, p. 136.

[298] _Quart. Journ. Micr. Soc._ xx. p. 443.

[299] _Quart. Journ. of Conch._ i. p. 368.

[300] _British Conchology_, i. p. xxviii.

[301] _Science Gossip_, 1865, p. 259.

[302] _Mollusques de France_, i. p. 130.

[303] _E.g._ Sochaczewer, _Zeits. wiss. Zool._ xxxv. p. 30.

[304] _Zool. Anz._ 1882, p. 472.

[305] _Zoologist_, iv. p. 1266.

[306] _Journ. Mar. Biol. Ass._ N.S. i. p. 217.

[307] Moquin-Tandon, _Moll. de France_, i. p. 133.

[308] _Zool. Jahrb. Anat._ iv. (1890) p. 501.

[309] Baudon, _Rév. Mag. Zool._ 1852, p. 575.

[310] _Arch. Zool. Exp. Gén._ (2) v. 1887, p. 2; compare also C. H. Hurst, _Natural Science_, ii. pp. 360, 421.

[311] Compare Pelseneer, _Bull. Sci. Fr. Belg._ (3) xix. pp. 107, 182.

[312] Pelseneer, _Arch. Biol._ viii. p. 723.

[313] Also known as _labial_ and _supra-oesophageal_ ganglia.

[314] Wivén, however (_K. Sv. Vet. Ak. Handl._ xxiv. 1892, No. 12), describes transverse connectives in _Chaetoderma_.

[315] στρεπτός, twisted; εὐθύς, straight.

[316] With the exception of _Actaeon_, which is streptoneurous (Bouvier, _Comptes Rendus_, cxvi. p. 68).

[317] This fusion of the cerebral and pleural ganglia and the consequent union of the cerebro-pedal and pleuro-pedal commissures can be recognised by sections of the mass (Pelseneer, _Comptes Rendus_, cxi. p. 245).

[318] There is practically no pharynx in the Pelecypoda, the mouth opening directly into the oesophagus.

[319] _Radere_, to scrape; ὸδούς, tooth; φέρειν, to carry.

[320] The mechanism of the radula has been dealt with by Geddes, _Trans. Zool. Soc._ x. p. 485. Rücker has observed (_Ber. Oberhess. Gesell. Nat. Heilk._ xxii. p. 207) that the radula in _Helix pomatia_ is the product of five rows of cells; the use of the first row is uncertain, the second forms the membrane of the radula, while rows three to five originate the teeth.

[321] _Jahrb. Deut. Malak. Gesell._ iii. p. 193.

[322] The whole of the radulae and jaws figured in this work are taken from the original specimens in the collection of the Rev. Prof. H. M. Gwatkin, who has always been ready to give me the run of his cabinets, which probably contain the finest series of radulae in the world. To his kindness I owe the following description of the process of mounting: “The first step is to obtain the radula. Dissection is easy in species of a reasonable size. On opening the head from above, so as to lay open the floor of the mouth, the radula itself is seen in most of the marine species, though in others it is contained in a sort of proboscis; and in the Pulmonata and others the student will find the buccal mass, with commonly a brown mandible at its front end, and the lingual ribbon in its hinder part. The teeth may be recognised by their silvery whiteness, except in a few cases like _Patella_ and _Chiton_, where they are of a deep brown colour. When obtained, the radula may be cleaned by boiling in a solution of caustic potash. There is no risk of injury if the solution is not too strong.

“Smaller species may be treated more summarily. The proboscis, the buccal mass, or even the whole animal may be thrown into the potash solution and boiled till scarcely anything is left but the cleaned radula. Remains of animals dried inside the shell may be similarly dealt with, after soaking in clean water. With a little care, this process will answer for shells down to the size of _Ancylus_ or _Rissoa_. The very smallest (_Carychium_, _Tornatellina_, _Skenea_, etc.) must be crushed on the slide and boiled on it, after removing as much as possible of the broken shell. The radula can then be searched for under the microscope, and washed and mounted on the slide.

“The student must be warned that though the general process is simple, there are difficulties in particular cases. In the Pulmonata, for example, membranes on both sides of the radula need careful removal. _Murex_, _Purpura_, and most of the _Taenioglossa_ have the side teeth folded down over the central, so that the arrangement is not well seen till they have been brushed back. The Cones, again, have no basal membrane at all, so that if the potash is not used with great care, the single teeth will fall asunder and be lost. Perhaps the worst case is where a large animal has a radula as small as that of a _Rissoa_, like _Turritella_, _Harpa_, or _Struthiolaria_, or where the radula is almost filmy in its transparency, like those of _Actaeon_ and the small _Scalaria_.

“When once the radula is laid out, the mounting is commonly easy. Canada balsam makes it too transparent. Fluids may be used, and are almost necessary for thick radulae like those of large _Chitons_; but the best general medium is glycerine jelly. It runs under the cover glass by capillary attraction, and may be boiled (though only for a moment) to get rid of air bubbles. It should then be left unfinished for several weeks. If cracks appear, the reason is either that the jelly is a bad sample, or that it has been boiled too long, or (commonly) that the object is too thick; and there is not often any difficulty in remounting. I have no serious complaint of want of permanence against the medium, if I may speak from a pretty wide experience during the last twenty years.”

[323] The substance both of the jaw and radula is neither crystalline nor cellular, but laminated. Chitin is the substance which forms the ligament in bivalves, the ‘pen’ in certain Cephalopoda, and the operculum in many univalves. Neither silica nor keratine enter into the composition of the radula.

[324] τόξον, arrow; ῥάχις, ridge, sharp edge; ταινία, ribbon; πτηνός, winged; γυμνὀς, bare; ῥιπίς, fan; δοκός, beam.

[325] _V. concinna_, according to Schacko (_Conch. Mitth._ i. p. 126, Pl. xxiv. f. 5); the lateral is large, strong, unicuspid on a broad base.

[326] In some cases (_e.g._ _Hyalinia inornata_) the laterals are very few, while in _Zonites laevigatus_ the first side tooth is more of a marginal than a lateral.

[327] Semon, _Biol. Centralbl._ ix. p. 80.

[328] According to Moquin-Tandon (_Moll. de France_, i. p. 44) this process in _Bithynia_ is attached by one end to the wall of the stomach. _Vivipara_, with two jaw pieces, does not possess this stylet; _Bithynia_, which does possess it, has no jaw.

[329] J. H. Vanstone, _Journ. Linn. Soc._ xxiv. p. 369.

[330] _Biol. Centralbl._ vii. p. 683; _SB. Ges. Nat. Fr._ 1890, p. 42; _Mag. Nat. Hist._ (2) v. 1850, p. 14.

[331] νεφρός, kidney.

[332] _Ann. Mag. Nat. Hist._ (2) xvi. p. 298.

[333] See, for instance, _Quart. Journ. Conch._ i. p. 340 (_Cyl. Raveni_): _Jahrb. Deut. Malak. Gesell._ 1879, p. 98 (_Clausilia dubia_).

[334] Cailliaud, _Journ. de Conchyl._ vii. p. 231; Gassies, _ibid._ p. 44.

[335] _Arch. Naturgesch._ xlii. p. 209.

[336] Dr. W. B. Carpenter, _Rep. Brit. Ass._ xiii. p. 71; xiv. p. 1; xvii. p. 93; J. S. Bowerbank, _Trans. Micr. Soc._ i. p. 123; Ehrenbaum, _Zeit. wiss. Zool._ xli. p. 1.

[337] See also p. 258.

[338] J. E. Gray, _Phil. Trans._ 1833, p. 774 f.

[339] J. E. Gray, _Phil. Trans._ 1833, p. 774 f.

[340] _Journ. de Conchyl._ iv. p. 424.

[341] _Journ. de Conchyl._ xii. p. 3.

[342] T. Scott, _Journ. of Conch._, 1887, p. 230.

[343] M. de Villepoix, _Comptes Rendus_, cxiii. p. 317.

[344] _Proc. Ac. Nat. Sc. Phil._, 1892, p. 350.

[345] Mr. B. B. Woodward has recently pointed out (P. Z. S. 1892, p. 528) a very remarkable method of shell absorption and growth in _Velates_ and certain other Neritidae.

[346] The only exception appears to be _Pedipes_, while in _Cassidula_ and _Scarabus_ the absorption is partial (Crosse and Fischer, _Journ. de Conch._ xxx. p. 177 f.).

[347] _Strombus_ and _Pteroceras_ (see Fig. 99, p. 200) exceptionally develop a siphonal notch which is distinct from the anterior canal.

[348] The _columella_, as distinct from the _columella lip_, is the solid pillar of shell round which the whorls are coiled (Fig. 177), the lower, or anterior portion of which alone is usually visible.

[349] J. E. Gray, _Phil. Trans._ 1833, p. 812.

[350] W. H. Dall, _Amer. Journ. Sc._ xxxviii. p. 445 f.

[351] The term _epidermis_, as distinct from _periostracum_, is properly restricted to the outer layer of the skin of the _mantle_ and body generally.

[352] J. Lewis, _Proc. Bost. Soc._ vi. p. 149.

[353] _Journ. of Conch._ v. p. 66.

[354] _The Dispersal of Shells_, pp. 182–195.

[355] E. A. Smith, _P. Z. S._ 1892, p. 259.

[356] C. T. Musson, _Proc. Linn. Soc. N. S. Wales_ (2), v. p. 883.

[357] _Scient. Results Sec. Yarkand Exped._ “Mollusca,” pp. 1–16.

[358] Mr. H. W. Kew, _The Dispersal of Shells_, has brought together a very large series.

[359] _The Naturalist in Nicaragua_, p. 334 f.

[360] Morelet, _Journal de Conch._ 1875, p. 194.

[361] Pollonera, _Boll. Mus. Zool. Torino_, v. 1890, No. 87.

[362] South and south-western France, however, belong to the Mediterranean Sub-region.

[363] The coast-line of north-east China, including Corea and Japan to north Niphon, is much more definitely tropical than the adjacent inland districts. The coast-line, therefore, must be placed in the Oriental Region, while the inland districts belong to the Palaearctic Region.

[364] _Biol. Centralbl._ ii. p. 208.

[365] Craven, _Journ. de Conchyl._ (3) xxviii. p. 101.

[366] _Jahrb. Deutsch. Malak. Gesell._ viii. p. 278.

[367] Netchayeff, _Kazan Soc. Nat._ xvii. fasc. 5.

[368] _Fauna der Congerien-Schichten_, p. 142.

[369] _Streptaxis_ is a remarkable instance of a _mainland_ genus. Although abundant in the Oriental, Ethiopian, and Neotropical regions, it never seems to occur on any of the adjacent islands, except in the case of Trinidad (1 sp.), which is practically mainland. _Omphalotropis_, on the other hand, is the exact reverse of _Streptaxis_ in this respect, occurring all over Polynesia and the Malay Is., as far west as Borneo, as well as on the Mascarenes, but never, save in a doubtful case from China, on the mainland of Asia, Australia, or Africa.

[370] The Amboyna group has been much the better explored. Common to both groups are one sp. each of _Kaliella_, _Trochomorpha_, _Opeas_, _Leptopoma_, _Cyclotus_, _Helicina_.

[371] A. H. Cooke, _P. Z. S._ 1892, pp. 447–469.

[372] Mysol, with 2 _Chloritis_, 1 _Insularia_, 1 _Cristigibba_, is decidedly Papuan.

[373] See especially C. Hedley, Note on the Relation of the Land Mollusca of Tasmania and New Zealand, _Ann. Mag. Nat. Hist._ (6) xiii. p. 442.

[374] Hedley and Suter, _Proc. Linn. Soc. N. S. Wales_ (2), vii. p. 613. Twenty-one species are “introduced.”

[375] Nine species have been introduced: 6 from Europe, 2 from the West Indies, 1 from the Western Isles.

[376] It is by no means implied that _unbroken_ land communication between India and Madagascar, across the Indian Ocean, ever existed. A series of great islands, whose remains are attested by the Chagos and other banks, would be quite sufficient to account for the results, as we find them. See especially Medlicott and Blanford, _Geology of India_, vol. i. p. lxviii.

[377] _Journ. Cinc. Soc. Nat. Hist._ iii. p. 317. The number is doubtless susceptible of very considerable reduction, say by one-half at least.

[378] Simpson, _Amer. Nat._ xxvii. 1893, p. 354.

[379] Compare von Martens, _Malak. Blätt._ 1868, p. 169; von Ihering, _Nachr. Deutsch. Malak. Gesell._ 1891, p. 93.

[380] The distribution of some Pteropoda has been worked out by Munthe, _Bih. Svensk. Ak. Handl._ XII. iv. 2, by Pelseneer _“Challenger” Rep._, Zool. xxiii., and by Boas, _Spolia Atlantica_.

[381] _Bull. Mus. C. Z. Harv._ xiv. p. 202; xxiii. p. 34 f.

[382] See papers in _P. Z. S._ 1878–85.

[383] A break in this uniformity may be found underneath the course of a great oceanic current like the Gulf Stream, which rains upon the bottom a large amount of food. A. Agassiz (_Bull. Mus. C. Z. Harv._ xxi. p. 185 f.) explains in this way the richness of the fauna of the Gulf of Mexico as compared with that of the west coast of tropical America.

[384] On the western coasts of Europe and America, where the change in surface temperature is very gradual, _Purpura lapillus_ (the west American ‘species’ are at best only derivatives) is able to creep as far south as lat. 32° (Mogador) in the former case, and lat. 24° (Margarita Bay) in the latter, the mean annual temperature of the surface water being 66° off Mogador, with an extreme range of only 8°, and that of Margarita Bay 73°, with an extreme range of only 5°. On the eastern coasts, where the Pacific and Atlantic gulf-streams cause a sudden change of temperature, the _Purpura_ is barred back at points many degrees farther north, _viz._ at lat. 41° (Hakodadi), surface temperature 52°, extreme range 25°; and at lat. 42° (Newhaven), surface temperature 52°, extreme range 30°.

[385] E. A. Smith, _P. Z. S._ 1890, pp. 247, 317.

[386] A. H. Cook, _Ann. Mag. Nat. Hist._ (5) xviii. (1886) p. 380 f; E. A. Smith, _P. Z. S._ 1891, p. 391 f.

[387] C. Keller, _Neue denksch. Schw. Gesell._ xxviii. 1883, pt. 3.

[388] According to Tate (_Trans. Roy. Soc. S. Austr._ 1887–88, p. 70), ‘Australian’ species predominate at Freemantle (32°), but Tenison-Woods (_J. Roy. Soc. N. S. Wales_, xxii. p. 106) holds that the tropical fauna extends as far south as Cape Leeuwin (34°), and that the Australian forms are not predominant until the extreme south. Tenison-Woods regards Cape Byron (31°) as the limit of the tropical fauna on the east coast, while some characteristic tropical genera reach Port Jackson, and a few (_e.g._ _Cypraea annulus_) Tasmania.

[389] A full account of the distribution of _Voluta_ is given by Crosse, _Journ. de Conchyl._ (3) xix. p. 263.

[390] Usually known as ‘Patagonian,’ but since the Magellanic Sub-region includes a considerable part of Patagonia, and since the greater part of sub-region (6) lies out of Patagonia, it has been thought advisable to change the name.

[391] _Amer. Nat._ xx. p. 931.

[392] W. H. Dall, _Proc. Biol. Soc. Washington_, v. p. 1 f.

[393] _Trans. Connect. Acad._ v. p. 177; _Zoologist_, 1875, p. 4502.

[394] _Rep. Scotch Fish._ iii. 1885, App. F, p. 67.

[395] _Nautilus_, vi. 1892, p. 82.

[396] _Journ. Mar. Zool._ i. pp. 3, 9.

[397] _Rep. Brit. Assoc._ 1844, Transactions, p. 74; _P. Z. S._ 1839, p. 35.

[398] It is convenient, but not morphologically correct, to apply the terms ‘ventral’ and ‘dorsal’ in this sense.

[399] φραγμός, partition; σήπιον, cuttle-bone; χόνδρος, long cartilage.

[400] μυέω, close the eyes; ὕψις, sight; contrasted with Oigopsidae (οἰγω, open).

[401] The classification is that of Foord, _Catal. Fossil Cephal. Brit. Mus._, 1888.

[402] Saville Kent, _Proc. Roy. Soc. Queensland_, vi. p. 229.

[403] J. Power, _Ann. Mag. N. H_. (2) xx. p. 334; _P. Z. S._ 1836, p. 113; _Arch. Zool. Exp. Gén._ (3) i. 1893, p. 105.

[404] In deference to Bergh’s high authority, the position of a sub-order is here given to the Ascoglossa. It may be doubted whether that position will stand the test of further investigation, and whether the families concerned will not be added to the Cladohepatic Nudibranchs.

[405] This family has also been classified with the Bulloidea and with the Aplysioidea.

[406] It appears more convenient to treat the whole group together, rather than deal with the two sections separately.

[407] An operculum is said to exist in the young forms of _Auricula_ and _Parmacella_.

[408] _Proc. Ac. Philad._ 1892, p. 390.

[409] Compare Jackson, _Amer. Nat._ xxv. p. 11 f.

[410] “A Monograph of the British Fossil Brachiopoda,” _Palaeontographical Society_, London, vols. i.-v. 1851–84.

[411] _Ibid._ vol. vi. 1886.

[412] “Contributions to the Anatomy of the Brachiopoda,” _Proc. Roy. Soc._, vol. vii.

[413] “Untersuchungen über den anatomischen u. histologischen Bau der Brachiopoda Testicardinia,” _Jenaische Zeitschrift_, vol. xvi., 1883.

[414] “On a living Spinose _Rhynchonella_ from Japan,” _Ann. Mag. Nat. Hist._, 5th ser., vol. xvii., 1886

[415] _Loc. cit._ p. 465.

[416] Shipley, “On the Structure and Development of Argiope,” _Mitt. aus d. Zool. Stat. zu Neap._ Bd. iv. 1883.

[417] Schulgin, “Argiope Kowalevskii,” _Zeit. f. wiss. Zool._ Bd. 41, 1885.

[418] _American Jour. of Sci. and Arts_, 3rd series, vol. xvii. 1879.

[419] _Loc. cit._ p. 470.

[420] “Recherches sur l’Anat. des Brachiopodes Inarticules,” _Arch. Zool. Exp._ (2), Tome iv., 1886.

[421] “Untersuchungen über den Bau der Brachiopoden,” Jena, 1892.

[422] “Vorläufige Mittheilungen über Brachiopoden,” _Zool. Anz._ Bd. viii. 1885.

[423] Hancock’s nomenclature is here used. The corresponding names used by King and Brooks are placed in brackets. Their nomenclature is used by many palaeontologists, and is adopted in Fig. 322.

[424] _Development of the Brachiopoda_, 1873 (Russian).

[425] “Histoire de la Thécidie,” _Ann. d. Sci. Nat._, Sér. 4, vol. xv., 1861.

[426] “On the Early Stages of Terebratulina septentrionalis,” _Mem. Boston Soc. Nat. Hist._, vol. ii., 1869. “On the Development of Terebratulina,” _Ibid._ vol. iii., 1873.

[427] “Choses de Nouméa,” _Arch. d. Zool. exp. et gen._, 2nd ser., vol. ix., 1891.

[428] J. Barrande, _Syst. Silur. Bohème_, vol. v., 1879. Hall and Clarke, _Introd. Palaeozoic. Brach._ (_Palaeont. of New York_, 1892–1894). Davidson, _Monogr._ _Brit. Foss. Brach._ (_Palaeont. Soc._, 1851–1884). Waagen, _Salt Range Fossils_ (_Mem. Geol. Surv. India_, 1879–1885).

[429] The results of the investigations of King (_Ann. Mag. Nat. Hist._, 4th ser., vol. xii., 1873) and of Brooks (_Chesapeake Zool. Laboratory, Scientific Results_, p. 35, 1879), and the simple nomenclature of these authors are here followed in preference to those of others, owing to the difference of opinion amongst anatomists of the functions and homologies of the muscles. The lateral muscles enable the valves to move backwards and forwards on each other; the centrals close the shell; the umbonals open it; and the transmedians allow a sliding sideways movement of one valve across the other (see also p. 477).

[430] Davidson and King, _Quart. Jour. Geol. Soc._, xxx. (1874), p. 124.

[431] _Amer. Jour. Science_, 1890–1893.

Transcriber’s Notes:

1. Obvious printers’, punctuation and spelling errors have been corrected silently.

2. Where hyphenation is in doubt, it has been retained as in the original.

3. Some hyphenated and non-hyphenated versions of the same words have been retained as in the original.

4. Superscripts are represented using the caret character, e.g. D^r. or X^{xx}.

5. Italics are shown as _xxx_.

6. Bold print is shown as =xxx=.