CHAPTER XV.
THE SKELETON OF THE CROCODILE.
The species chosen for description is C. palustris, a form occurring throughout the Oriental region, but the description would apply almost equally well to any of the other species of the genus Crocodilus, and with comparatively unimportant modifications to any of the living Crocodilia.
I. EXOSKELETON.
The exoskeleton of the Crocodile is strongly developed and includes elements of both epidermal and dermal origin.
a. The epidermal exoskeleton is formed of a number of horny scales or plates of variable size covering the whole surface of the body. Those covering the dorsal and ventral surfaces are oblong in shape, and are arranged in regular rows running transversely across the body. The scales covering the limbs and head are mostly smaller and less regularly arranged, and are frequently raised into a more or less obvious keel. Those covering the dorsal surface of the tail are very prominently keeled.
The epidermal exoskeleton also includes the horny claws borne by the first three digits of both manus and pes.
b. The dermal exoskeleton. This has the form of bony scutes which underlie the epidermal scales along the dorsal surface of the trunk and anterior part of the tail. Except in very young individuals the epidermal scales are rubbed off from these scutes, which consequently come to project freely on the surface of the body. Each scute is a nearly square bony plate, deeply pitted or sculptured, and marked by a strong ridge on its dorsal surface, while its ventral surface is smooth. Contiguous scutes are united to one another by interlocking sutures.
The scutes are arranged in two distinct areas, viz. (1) a small anterior nuchal shield which lies just behind the head and is formed of six large scutes more or less firmly united together, and (2) a larger posterior dorsal shield covering the whole of the back and anterior part of the tail, and formed of smaller scutes, which are arranged in regular transverse rows, and progressively diminish in size when followed back.