REPTILES. 



sion of the jaws into horn-clad beaks. Certain representatives of the extinct 

 flying dragons were likewise devoid of teeth; and as in these forms the horn- 

 covered jaws were long and narrow, the resemblance to the beak of a bird becomes 

 most marked. 



It has already been stated that the vertebras of Reptiles never articulate by 

 means of those saddle-shaped surfaces so characteristic of Birds. They present, 

 however, great diversity of structure in this respect. In some cases, for instance, 

 as in the fish-lizards, the bodies or central portions of the vertebras are very short 



from front to back, and have concave surfaces 

 both in front and behind for mutual articula- 

 tion. In marked contrast to this type is the 



LEFT-SIDE VIEW OF A NECK VERTEBRA. 

 OF A DINOSAUR. 



b, anterior ball. — After Marsh. 



SIDE AND FRONT VIEWS OF THE BODY 

 OF A FISH-LIZARD. 



)F A VERTEBRA 



a, b, attachment of ribs. 



neck vertebra of a Dinosaur, where the anterior end of the body of each vertebra 

 forms a convex knob (b), received into a cup at the posterior end of the vertebra 

 in advance. 1 In other instances, as in the existing crocodiles and lizards, an 



arrangement pre- 

 cisely the reverse 

 of the last is pre- 

 sent ; that is to 

 say, the ball is at 

 the hinder end, and 

 the cup at the front 

 of the body of the 

 vertebra. In a 

 few lizards and in 

 all snakes the ver- 

 tebras are further 

 complicated by the 

 development of 

 additional articular facets, taking the form of wedge-like projections from one 

 vertebra, which are received into cavern-like excavations in the adjacent one. 



1 It should be mentioned that in this figure only the portion of which b is the extremity corresponds with the 

 whole of the specimen represented in the other figure on the same line. 



FRONT AND BACK VIEWS OF A VERTEBRA OF A SNAKE. 



zi indicates the additional articular process, which is received into the cavity zi 1 . 



