592 S. W. WILLISTON 



projection anteriorly, agreeing rather better with the pariotichid 

 type. The symphysis is continuous or nearly so throughout, 

 without a median puboischiadic interval. The sacrum has three 

 pairs of large sacral ribs, agreeing in this respect with the Clep- 

 sydropidae, and very different from the Poliosauridae, which have 

 but two pairs. The spines of the vertebrae of the basal caudal, 

 sacral, and lumbar regions at least are low cylindrical, with a nodular 

 extremity, quite unlike the elongated forms of the Clepsydropidae 

 and the moderately elongated and flattened spines of the Polio- 

 sauridae. Evidently the short co-ossified ribs of the lumbar 

 regions are united to both arch and sacrum, and the ribs more 

 anteriorly have double heads. None of the spines are elongated, 

 as is indicated by numerous isolated vertebrae found in the wash. 

 The femur (Fig. i, B, C, D, E), tibia (Fig. i, F, G, H, I), and 

 fibula (Fig. i, J, K, L, M) are sufficiently well shown in the figures. 

 They are all much heavier and shorter than the corresponding 

 bones of Varanosaurus. Of the feet (Fig. i, N) I figure only those 

 bones which were found in natural articulation; the remainder 

 were detached in the feet studied. The phalangeal formula, as 

 in Varanosaurus and Dimetrodon, is 2, 3, 4, 5, 4. The foot differs 

 materially from that of Varanosaurus and its allies in the large size 

 of the fifth digit. The second centrale is well ossified, whereas in 

 Varanosaurus it was small in both front and hind feet and remained 

 cartilaginous throughout life. It is very evident also that the foot 

 was placed at a greater angle with the leg in walking. That the 

 animal was of the crawling, lizard-hke habit and form is undoubted. 

 The present genus in all probability belongs to the order Pely- 

 cosauria as at present bounded. Nevertheless the marked dif- 

 ferences in the pelvis may indicate corresponding differences in the 

 skull. Furthermore I protest against the union of the Poliosauridae, 

 or Varanosaurus at least, in the same group with Dimetrodon or 

 Naosaurus. The structure of the skull, with no lower temporal 

 arcade, aside from other characters of the skeleton sufficiently 

 justifies a subordinal position. 



Trispondylus texensis, genus and species new. 



A new genus and species of reptile is represented in the Chicago 

 collection by a considerable part of a skeleton collected by Mr. 



