1 98 



WATER REPTILES OF THE PAST AND PRESENT 



attachment of the short " hatchet-shaped" ribs, much lateral 

 movement of the neck is prohibited, nor is any very great vertical 

 movement possible. The vertebrae of the whole column, save the 

 atlas, the second sacral, and the first caudal — which is a very re- 

 markable anomaly — are concave in front and convex behind, agree- 

 ing in this respect with those of all other living reptiles, save the 

 turtles, the tuatera, and some lizards. The ribs of the neck have 

 their two heads attached, one to the body of the vertebra, the 

 other to the arch, but those of the dorsal region, though double- 

 headed, have both become attached to the transverse projection of 

 the arch, a seemingly trivial character, but one which immediately 

 distinguishes all crocodiles from all other water reptiles, and from all 



Fig. ioi. — Vertebrae of gavial from the side (cervical), and from in front (dorsal) : 

 az, anterior zygapophysis; pz, posterior zygapophysis; d, diapophysis ; r, cervical rib; 

 c, articulation for head; /, for tubercle of dorsal rib. 



terrestrial reptiles, indeed, save the Parasuchia, Pterosauria, and 

 Dinosauria. The pelvis is firmly attached to the spinal column by 

 two sacral vertebrae. 



The collar-bones, or clavicles, are wanting in crocodiles; there 

 is a slender interclavicle; and the shoulder-blade and coracoid are 

 well developed (Fig. 102). The bones of the pelvis are loosely 

 united with each other as they are in most reptiles (Fig. 104) . The 

 pubes, the anterior bones below, unlike those of all other reptiles, 

 do not help to form the acetabulum or socket for the articulation of 

 the thigh bone, nor do they articulate with each other. This 

 single character sharply distinguishes a crocodile from all other 

 reptiles, living or extinct, and is almost the only character that 



