600 



EEPTILIA 



[CH. 



backwards, the capitular attachment to the centrum is gradually 

 raised till it reaches the transverse process and is confounded with 

 the tubercular attachment, and the hindermost vertebrae are single 

 headed. There are abdominal ribs, as in Sphenodon ; they are 

 arranged in transverse rows, each row on each side consisting of 

 three or four bones (Fig. 299). 



The pectoral girdle consists of simply a scapula and coracoid, 

 the latter reaching the sternum, which is cartilaginous but protected 

 ventrally by an interclavicle (Fig. 300). In the fore-limb the carpus 

 has retained three bones in the proximal row, but the distal row 



consists of a block of car- 

 tilage representing the first 

 and second carpalia and a 

 bone representing the re- 

 maining three. There is 

 consequently an intercarpal 

 wrist joint corresponding to 

 the intertarsal joint com- 

 mon to Reptiles. 



The pelvic girdle is very 

 peculiar. The ilium is 

 broad and rounded above 



and joins the two sacral 

 1. Neural spine of atlas. 2. Lateral portion of rpv v j 



atlas. 3. Odontoid process. 4 Ventral vertebrae. The pubis does 



portion of atlas. 5. Neural spine of axis. not form any part of the 



6. Postzygapophysis of fourth vertebra, i j /. ,1 



7. Tubercular portion of fourth cervical rib. ndary the aceta- 



8. First cervical rib. 9. Second cervical bulum or socket for the 

 rib. 10. Convex posterior surface of i j /> ,1 f mi 

 centrum of fourth vertebra. head of the femur. This 



is completed by a small 



bone termed the acetabular bone. This exclusion of the pubis 

 from the boundary of the acetabulum is a feature of modern 

 Crocodiles, because in extinct Crocodiles the pubis took its proper 

 share in forming the border of the acetabulum. The tarsus, like the 

 carpus, is much reduced and modified. It consists of a proximal 

 row of two bones, one of which, the fibulare or calcaneum, forms 

 a distinct heel. The distal row consists of two bones, one repre- 

 senting the first, second and third tarsalia, the other the fourth 

 and fifth. 



The heart of the Crocodile is remarkable for the fact that the 

 septum in the ventricle has grown forwards so as to completely 

 divide it into two halves, the right and left ventricles. The left 



FIG. 298. First four cervical vertebrae of a 

 Crocodile, C. vulgar is. Partly after von 

 Zittel. 



