FOSSIL REPTILES. 297 



scales of the skin are generally small, without crests, and with- 

 out spines, though they possessed them in the former tail ; and 

 internally, instead of the numerous vertebrae, with all their 

 apparatus of apophyses and ligaments, there is nothing but a 

 long cartilaginous cord, all of a piece, and exhibiting only 

 numerous annular wrinkles of no great projection. 



The sternum of lizards forms with the shoulder a sort of cui- 

 rass for the protection of the heart and large vessels. It is more 

 complicated than in the crocodiles, and on a different plan from 

 that of the tortoises. It consists essentially in a long, narrow, 

 depressed bone, which gives out in front two branches directed 

 on each side, and between which its point sometimes passes, 

 and proceeds more in front under the neck. This bone, from 

 its hinder part, penetrates into a cartilaginous lamina, of a 

 rhomboidal form, which has two sides in front, and two behind, 

 and often exhibits traces of a longitudinal division into two 

 halves. 



Its anterior sides are continued with the edges of the anterior 

 part of the bone, but departing a little to the right and left. 

 They are sometimes ossified, particularly their edge, which 

 has a groove, supporting, like a mortise, the sternal edge of 

 the clavicular bone. The hinder sides of the rhomboidal car- 

 tilage serve for the insertion of the false ribs. Hitherto there 

 is little difference between the conformation of this sternum 

 and that of the crocodiles, except in the anterior branches of 

 the oblong bone, which give it the figure of a T, of an arrow, 

 or a cross, according to the species. 



A more considerable difference, however, consists in the 

 development of the coracoi'd bone, and in the constant pre- 

 sence of a clavicle of greater or less size. The coracoid fur- 

 nishes nearly one half of the glenoid foss. But its principal 

 peculiarity is giving out one or two apophyses to support a 

 large cartilaginous arch, which passes over the narrow bone in 

 front of the sternum, and crosses with that of the coracoid on 

 the other side. This singular crossing, which is found even 



