CHAPTER II 



THE SKELETON 



A. The Exoskeleton 



THE exoskeleton is well developed in the 

 Crocodilia, and forms a very considerable 

 protection to its bearer. It is both dermal 

 and epidermal in origin. 



The epidermal skeleton of the alligator consists of 

 oblong horny scales, arranged in transverse rows; 

 the long axes of the scales are parallel to that of the 

 body. On the tail, except along the mid-dorsal 

 line, and on the ventral side of the trunk and head 

 these scales are very regular in outline and arrange- 

 ment; on the sides of the head and trunk and on 

 the legs they are much smaller and less regularly 

 arranged, while along the mid-dorsal line of the 

 tail, especially in its posterior half, they are ele- 

 vated into tall keels that give the tail a large 

 surface for swimming. The first three digits of 

 both manus and pes are armed with horny claws, 

 which also belong to the epidermal part of the 

 exoskeleton. 



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