Case and Willi ston — -Description of Reptilian Skulls. 341 



to accommodate the wide sockets for the teeth. The outer por- 

 tion, forming the sides of the facial region, is thin and marked 

 with a sculpture of tine pits. The swollen portion departs 

 abruptly from the inner side, forming a gently swelling promi- 

 nence ; from a point near the middle of the inner side of this 

 swollen portion rises the palatine process of the maxillary 

 which projects from the bone at a fairly steep angle and leaves 

 a deep groove between it and the bone proper. The process 

 is thin and the lower edge is slightly rugose. It extends in a 

 gentle curve, following the outline of the inner edge of the 

 maxillary, from the third or fourth tooth to beyond the last 

 tooth. The character of this process has been in doubt, Cope 

 and Case believing that it might possibly be the palatine bone, 

 but the condition of this specimen leaves no doubt of its true 

 nature. There are 11 maxillary teeth ; the first has the form 

 of the incisors except that the face is not so broad and chisel- 

 like. It is smaller than the incisors and there is no approach 

 to a canine character. The second is smaller than the first 

 and more conical in form. Both of these are nearly vertical. 

 The succeeding teeth, except the last, have the characteristic 

 transverse widening ; the first of these, the third of the series, 

 has a sharp median cusp and the inner and outer edges are 

 rounded ; the rest, except the eleventh, have a median cusp and 

 lateral cusps on the inner and outer edges, identical with the 

 teeth of Diadecies phaseolinus Cope. The teeth increase in 

 width to the sixth or seventh and then decrease to the poste- 

 rior end. The eleventh is not preserved, but the outline of the 

 base shows it to have been small and conical. When first 

 erupted the enamel of the teeth was marked by rugose lines 

 which radiate from the central cusp, but these are soon removed 

 by wear, and in old individuals the surface is nearly flat. 

 There is a deep pit on the inner side of the base of each of the 

 teeth, marking the position of successional teeth. 



The prevomers (vomers) are paired and articulate strongly 

 with the premaxillaries in front, the pterygoids behind, and 

 the palatines laterally. They are of considerable vertical 

 extent and closely applied to each other in the median line. 

 Case (Publication 145, Carnegie Institution, p. 71) has described 

 the posterior ends of the pre vomers as spreading apart above 

 at the posterior end and receiving the lower edge of the eth- 

 noid. It is now apparent that this open portion is the anterior 

 end of the pterygoids or the posterior of the palatines. The 

 lower surface of the prevomers is flat and there is a series of 

 small, sharp, conical teeth about a millimeter in length. The 

 posterior limit can not be determined as the suture between 

 the prevomer and the pterygoid is not distinguishable. 



The. palatines are gently convex upward ; the outer edge is 



