The Skeleton 47 



The dermal exoskeleton consists of bony scutes 

 that underlie the epidermal scales of the dorsal sur- 

 face of the trunk and anterior part of the tail. The 

 overlying scales, except in very young animals, 

 are always rubbed off, so that the bony scales 

 are exposed. The ventral or inner surface of the 

 scutes is flat, while the outer surface is strongly 

 keeled and in old animals is often rough and pit- 

 ted. The plates are nearly square in outline and 

 are closely joined together in most places. 



The scutes are grouped in two fairly distinct 

 areas known as the nuchal and the dorsal shields. 

 The former lies just back of the head, in the region 

 of the fore legs, and consists of four larger and a 

 number of smaller plates (Fig. 15). The latter, or 

 dorsal shield, extends over the back in fairly regular 

 longitudinal rows and quite regular transverse 

 rows. At the widest part of the trunk there are 

 six or eight of these scutes in one transverse row. 

 They become smaller towards the tail. 



The teeth are exoskeletal structures, partly of 

 ectodermal, partly of dermal origin. They are 

 conical in shape, without roots, and are replaced 

 when lost. They will be described in connection 

 with the skull. 



Musk glands, said by Gadow to be present in all 

 Crocodilia, are found in both sexes and are deriva- 

 tions of the skin. One pair, each of which may be 

 as large as a walnut, is found on the lower side of 

 the head, one on the inside of each half of the 



