SKELETON OF THE CROCODILE. VERTEBRAL COLUMN. 243 



THE SACRAL VERTEBRAE. 



These are two in number, and while the centrum of the 

 first is concave in front (fig. 42, B, 6) and nearly flat behind, 

 that of the second is flat in front and concave behind. Each 

 has a pair of strong ribs (fig. 42, B, 4) firmly ankylosed in the 

 adult with a wide surface furnished partly by the centrum, 

 partly by the neural arch. The distal ends of these ribs are 

 united with the ilia. The character of the neural spines and 

 zygapophyses is the same as in the thoracic vertebrae. 



THE CAUDAL VERTEBRAE. 



These are very numerous, about thirty-four in number. 

 The first differs from all the other vertebrae of the body in 

 having a biconvex centrum. The succeeding ones are procoe- 

 lous and are very much like the posterior thoracic and lumbar 

 vertebrae, having high neural spines and prominent straight 

 transverse processes. They differ however in having the 

 neural spines less strongly truncated above, and the transverse 

 processes arise from the centra and not from the neural 

 arches. When followed further back the centra arid neural 

 spines gradually lengthen while the transverse processes be- 

 come reduced, and after the twelfth vertebra disappear. 

 Further back still the neural spines and zygapophyses 

 gradually become reduced and disappear, as finally the neural 

 arch does also, so that the last few vertebrae consist simply of 

 cylindrical centra. 



Each caudal vertebra, except the first and the last eleven 

 or so, has a V-shaped chevron bone attached to the postero- 

 ventral edge of its centrum. The anterior ones are the largest 

 and they gradually decrease in size till they disappear. 



B. THE SKULL 1 . 



The skull of the Crocodile is a massive depressed structure 



1 Free use has been made of L. C. MialPs Studies in Comparative 

 Anatomy, i., The Skull in Crocodilia, London, 1878. See also W. K. 

 Parker, Tr. Z. S. t vol. xi. 1885, p. 263. 



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