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 
