the radiale, ulnare, pisiform, and fourth carpale, as they are usually called. The radiale is very large and elongate, dilated at its ends and articulating with the radius and preaxial border of the ulna. It is supposed to be the fused radiale and intermedium but possibly is the intermedium only. The ulnare, of similar shape, but smaller, is approximated to the middle part of the distal border of the ulna, articulating also with the pisiform and radiale; distally with the fourth carpale only. The pisiform, of considerable size, articulates with the postaxial border of the ulna and ulnare. The first three carpalia, and perhaps also the centrale, are represented by cartilage, which fills out the interval between the end of the radiale and the metacarpals. This structure is a very ancient one as shown in the carpus of Alligatorellus (Fig. 140 b) and Crocodeleimus from the Jurassic, where, indeed, the two carpals are yet more elongate.
Fig. 140. Limbs: A, Alligator (Crocodilia). One half natural size. B, Alligatorellus (Crocodilia). Twice natural size. C, D, Amblyrhynchus (Lacertilia). Natural size.
