122 



low large animals whole, but arc not furnished at the same time with the 

 arrangement of the suspensorium, the quadrate, and mandible, by which they 

 unfold downward, thus increasing the vertical diameter of the pharyngeal 

 cavity. The palatine and maxillary arches not having the mobility seen in 

 snakes, the mandibles possess increased adaptation to the necessities of doubt- 

 less similar habits. 



The accompanying cut shows the appearance of the normal flexure of 

 the ramus: c is the splenial articulation ; d, the coronoid process; and e, the 

 quadrate cotylus. 



.A A A A A A A A A A A 



Fig. 4. — Eight mandibular ramus of Clidastcs propyllwn, Cope, one-third natural size: a, from tho 

 inner side; b, from above. Fig. 5. — Left ramus of Loxocemus bicolor, a pythouid from Central America, 

 inner side, natural size. Fig. (i. — Right ramus of Enjx johnii, Euss., from India, inner side, natural size. 

 1, articular; 2, surangular; 3, angular; 4, corouoid; 5, splenial; G, deutary. 



Vertebra and ribs. 



Verlebrce. — As has been already pointed out by Cuvier, the vertebra; in 

 Mosasaurus Tall into cervical, dorsal, sacro-lumbar, and caudal scries. The 

 cervicals are either round or depressed ; they are arbitrarily characterized by 

 the presence of an obtuse hypapophysis, which has an articular surface for a 

 separate continuation of the same. The latter may be compared to short, 

 compressed, ungueal phalanges. The articular extremity of some is nearly 

 plane; of others, conic, with antero-posterior enlargement. They are directed 

 posteriorly, and have a broad, obliquely ovate outline on the lateral view. 

 Their extremities are rugose. 



The atlas consists of the three pieces, the basal and two lateral. The 

 axis supports a large odontoid process, which is bounded below by a tlirce- 

 sided piece, which is provisionally called its hypapophysis. Besides these, 

 lie axis has its own proper fixed and corresponding free hypapophyses. 



