OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 375 



mandibles are preserved in position with the maxillae entire, show- 

 ing that the premaxillae must have been small, with not more than 

 two teeth in each. 



The occiput is clearly distinguishable in two skulls, and partially 

 so in a third. It has a smooth declivity on each side between the 

 angular median projection and the foramen magnum on the inner 

 side, and the parietal arch on the outer side. The surface, descend- 

 ing nearly to the lower border of the foramen magnum, is clearly 

 distinguishable from the dorsal surface and the tabulare, although 

 no distinct post-temporal vacuity is visible; probably in life there 

 was a small vacuity here, which has been obliterated by the depres- 

 sion of the arch. At the outer side the thin bone abuts against 

 the distal end of the tabulare, and thus must come in contact with 

 the upper end of the quadrate. I can distinguish no sutural divi- 

 sions on this surface, though doubtless it must be formed by the 

 supraoccipital, paroccipital, and exoccipital. I am very skeptical 

 of some of the recent interpretations of the structure of the occipital 

 region of certain American Permian reptiles. It cannot be said 

 too emphatically that only under the most exceptional circum- 

 stances can sutures be determined with any degree of certainty 

 from single specimens. The foramen magnum is large; the 

 occipital condyle is hemispherical. 



The details of the palate are less certainly determinable. There 

 is an interpterygoidal vacuity, with low, conical teeth along the 

 pterygoids and vomers in front. One specimen shows an indica- 

 tion of a median parasphenoid. The downwardly prominent 

 portion corresponding to the transverse bone— if it be distinct — 

 is armed with five conical teeth of a size nearly as large as those on 

 the anterior part of the maxilla; this elevation joins the maxilla 

 just back of the teeth. Back of these transverse rows of teeth 

 there is an elongated basisphenoid, with a shallow cavity in the 

 middle and a low basisphenoid tuberosity on each side at the end 

 of a lateral elevation. 



The teeth of Araeoscelis either are variable or the material that 

 I have assumed to belong to a single species comprises more than 

 one. Without better evidence to the contrary, however, I shall 

 assume that the differences which they present, like those of the 



