VERTEBRA. OF THE CROCODILE. 101 



centrum is concave ; in the second, it is the posterior sur- 

 face ; the zygapophyses are not obliterated in either of 

 these sacral vertebra, so that the aspects of their articular 

 surface — upwards in the anterior pair, downwards in the 

 posterior pair — determines at once the corresponding ex- 

 tremity of a detached sacral vertebra. The thick and 

 strong transverse processes form another characteristic of 

 these vertebrae ; for a long period the suture near their 

 base remains to show how large a proportion is formed 

 by the pleurapophysis. This element articulates more 

 with the centrum than with the diapophysis developed 

 from the neural arch ; it terminates by a rough, truncate, 

 expanded extremity, which almost or quite joins that of 

 the similarly but more expanded rib of the other sacral 

 vertebrae. Against these extremities is applied a sup- 

 plementary costal piece, serially homologous with the 

 appendage to the proper pleurapophysis in the dorsal 

 vertebrae, but here interposing itself between the pleura- 

 pophyses and haemapophyses of both sacral vertebra, 

 not of one only. This intermediate pleurapophysial 

 appendage is called the "ilium;" it is short, thick, 

 very broad, and subtriangular, the lower truncated apex 

 forming with the connected extremities of the haemapo- 

 physis an articular cavity for the diverging appendage, 

 called the "hind leg." The hajmapophysis of the an- 

 terior sacral vertebra is called " pubis," 64 ; it is mode- 

 rately long and slender, but expanded and flattened at 

 its lower extremity, which is directed forwards towards 

 that of its fellow, and joined to it through the inter- 

 medium of a broad, cartilaginous, haemal spine, com- 

 pleting t*he haemal canal. The posterior h^emopophysis, 

 63, is broader, subdepressed, and subtriangular, expand- 

 ing as it approaches its fellow to complete the second 



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