306 YERTEBRATE ANIMALS. 



flight. The wings are long and pointed, the sternal keel is greatly 

 developed, the pectoral muscles are of large size, and many of them 

 exhibit powers of locomotion more rapid than those enjoyed by any 

 other members of the animal kingdom. 



SUB-CLASS in. ODONTORNITHES. 



Order I. Saurur.e. 



This order includes only the single extinct Bird, the Archoeopteri/jr, 

 ■which has been found in the Oolitic rocks of Germany. The Archce- 

 opteryxvi&a about as big as a common Rook, and shows many singular 

 points of resemblance to the true Reptiles. It diflFei-s from all living 

 birds in having two free claws to the wing, and in possessing a long 

 lizard-like tail. Instead of the ploughshai-e-shaped bone which ter- 



Fig. 220. — Ai'chfEopteryx. Tail and detached bones. 



minates the tail in living birds (fig. 204, B), the tail in Archceopteryx 

 (fig. 2i0) is very long, and consists of about twenty distinct and 

 separate verteln-a^, each of which supports a pair of cpill-feathers. 

 The tail, tlierefore, except for (he presence of feathers, must have 

 been very like that of a Reptile. As in all the Birds of this sub- 

 class, the jaws A\ei-e furnished with conical pointed teeth. 



Order II. Odontolce. 



This order comprise.s only a singie extinct Bird, the extraordinary 

 ITj'xperornis rffudis of the Ci'etaceous rocks of North America, for 

 the discovery and description of which science is indebted to Pro- 



