*8 ELEMENTARY ANATOMY. [LESS. 



The third sub-class comprises two very aberrant genera 

 only. It is called ORNITHODELPHIA, and the animals com- 

 prised within it are termed Ornithodelphous mammals. It 

 consists of one order only : 



XIV. MONOTREMATA. Of this order 

 there are but two genera 

 one the Echidna, the other 

 the Duck-billed Platypus or 

 FIG. 24. THE DUCK-BILLED Ornithorhynchus. 



f**h* Tv^^T ves A v nta i ns al ! th i e 



Birds (or feathered Vertebrates). It 

 is a very uniform class, containing only three sub-classes. 



The first sub-class, the CARINAT/E, comprises all living 

 birds except those contained in the next sub-class, together 

 with the extinct Dodo and the Great Auk. 



The second sub-class, the RATnvE, includes the Ostrich, 

 Rhea, Emeu, Cassowary, Apteryx, and the extinct Dinornis 

 and its allies. 



The third sub-class, now extinct, the SAURUR^E, is as yet 

 only known to have contained that bird of the Oolite, the 

 Archaeopteryx. 



FIG. 25. THE OOLITIC FOSSIL BIRD FIG. 26. THE FRILLED LIZARD 



(A rclueopteryx). (Chlamydosaurus). 



The class Reptilia embraces all the scaly, featherless, cold- 

 blooded creatures, and consists of nine orders. 



I. CROCODILTA. An order containing only the Croco- 

 diles, Alligators, and Gavials. 



II. SAURIA. A very numerous group, containing all the 

 Lizards, some of which are without legs, and might 

 be taken for serpents : the two-armed Chirotes, 

 the two-legged Bipes, Lialis, the Amphisbena, the 

 Chameleons, Geckoes, Iguanas, Monitors, Seines 

 (Cyclodus, &c.), the Agamas, the flying lizard, Draco, 

 and the exceptional genus Sphenodon. 

 ill. OPHIDIA. In which are placed the harmless Snakes 



