174 



THE OSTEOLOGY OF THE REPTILES 



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 ap- 

 proximated to the middle part of the distal border of the ulna, articu- 



FiG. 1 40. Limbs: A, Alligator (Crocodilia). One half natural size. B, Alligatorellus (Croco- 

 dilia). Twice natural size. C, D, Amblyrhynchus (Lacertilia). Natural size. 



lating 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 Alli- 

 gatorellus (Fig. 140 b) and Crocodeleimus from the Jurassic, where, 

 indeed, the two carpals are yet more elongate. 



