CHAPTER V
THE SUBCLASS PROTOTHERIA OR ORNITHODELPHIA 117
General characters, 117. _Family_ ORNITHORHYNCHIDÆ, 119; _Ornithorhynchus_, 119. _Family_ ECHIDNIDÆ, 124; _Echidna_, 125; _Proechidna_, 126; Fossil species, 127.
THE SUBCLASS PROTOTHERIA OR ORNITHODELPHIA 117
General characters, 117. _Family_ ORNITHORHYNCHIDÆ, 119; _Ornithorhynchus_, 119. _Family_ ECHIDNIDÆ, 124; _Echidna_, 125; _Proechidna_, 126; Fossil species, 127.