8 



PBRMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



position of the quadrate bone in the lower bar of the otic opening and shows that 

 it did not form part of the posterior bar of the opening in Cacops. 



A careful examination of the bones of the temporal region of the left side shows 

 a series of lines, very certainly sutures, as they are different in character from 

 cracks which accompany them, and as some of them show, for a short distance, 

 the peculiar wavy form of sutures The course of these sutures and the relations 

 of the bones thus outlined are shown in fig. 3 a. Similarly the outlines of the 

 maxillaries, the lachrymals, and the jugals can be made out. From the strong 

 resemblance of the skull to that of Cacops, in other regards, it is probable that the 

 general course of the sutures was the same as in that genus. The otic notch is 

 widely open posteriorly and the surfaces of the bones bordering it are smooth; 

 but the adjacent portions of the skull, both on the sides and the top, are marked 

 by a fine sculpture and pitting. 



On the lower surface of the skull (fig. 3 b) the bones have the same general 

 form and relationships as described by Williston in Cacops. The occipital condyles 

 are well formed and inclined sharply backwards and inwards. The basisphenoid 



Fig. 3. — Aspidosaurus novomexicanus, No. 673, University of Chicago. X Jj. 



A, upper surface of skull, shaded parts restored; B, lower surface of skull; 



C, three dorsal vertebrae with attached armor plates. 



is well developed, with strong basipterygoid processes corresponding to the enlarge- 

 ment in the same position in Cacops. The basisphenoid was well ossified and 

 evidently as fully functional as in the Cotylosauria. The ophisthotics are pre- 

 served, but the inner ends, perhaps due to injury, do not have the broad and 

 fan-shaped form figured by Williston for Cacops. On the left side there is a 

 slender styliform bone near the anterior end of the otic notch, which is without 

 doubt the stapes, as it corresponds exactly in position with the same bone in 

 Cacops. Anteriorly the large rhinencephalic chamber lies detached, by injury, 

 from the basisphenoid, and on its lower surface lies the poorly developed para- 

 sphenoid. The lower jaws lie in position and most of the teeth are hidden, but a 

 few in the right jaw and more in the maxillary show them to have been slender 

 and conical; there is no evidence of any enlarged teeth, either in the upper or the 

 lower jaws. The matrix and the lower jaws conceal the anterior portion of the 

 palate, but so far as can be made out there is no trace of the large teeth which 

 appear on the palate of Cacops. 



The femora, humeri, scapulce, and the pelvis (lacking only the crest of the 

 ilium, as preserved) are indistinguishable from the same bones in Cacops. 



