398 



5. W. WILLISTON 



I give herewith an enlarged photograph of the specimen, which 

 will show, at a glance, the striking characteristics of the form; the 

 figure given by Cope is in some things incorrect and obscure. In a 

 very careful study of the specimen, I find no corrections of his rather 

 brief description, but there are some facts that I can add with assur- 

 ance. Positive indications of twenty-three dorsal vertebrae are pre- 

 sent, and, since the left manus is doubtless in its normal position on 



the block, it is hardly possible that there 

 could have been more than one or two 

 more, that is, the number is doubtless the 

 same as that of Sauravus. The ribs are 

 small, slender, and curved, moderately 

 dilated at the proximal extremity, but 

 without real differentiatioD into head and 

 tubercle; they are all attached interver- 

 tebrally. The vertebrae were certainly 

 amphicoelous, and doubtless with per- 

 sistent notochord, agreeing with those of 

 Sauravus, and the Microsauria generally. 

 The vertebral spines are rudimentary; 

 and there are no indications of any kind 

 of ventral ribs — one is safe in saying that 

 the animal in life had none — in this respect 

 differing from Sauravus. Nor is there 

 any distinct evidence of hypocentra, 

 though it is not impossible that such 

 bones of small size may have been present. 

 All the dorsal vertebrae bear ribs, and 

 the first three of the caudal series also. 

 Two vertebrae intervene without free ribs. On the left side the upper 

 border of an ilium is discernible, close to the sides of the centra, and 

 between them and the head of the femur. This ilium was certainly 

 united to these two vertebrae. There were two sacral vertebrae, as 

 in Sauravus, a reptilian character. The specimen lies on its ventral 

 side, and the pubes and ischia, hence, are not visible. The tail, 

 like the body, was evidently long and slender. 



The perfection of the hind limbs is such that scarcely any thing 



Fig. 2. — Left hind leg and 

 foot of Isodectes copei Will., 

 enlarged. 



