340 Case and Williston — Description of Reptilian Skulls. 



sutures can not be made out nor can any grooves such as fig- 

 ured by Williston (Am. Permian Verts., fig. 1 and pi. xxxviii) 

 be seen. In the specimen figured by Williston the bones 

 were separated and the sutures thus determined resemble very 

 closely those shown in the single specimen of Diadectes from 

 Texas, in which the sutures can be made out. Cope mentions 

 the occurrence of grooves on the skull of C/ulonyx, consider- 

 ing them to be the marks of attachment of corneous plates, 

 but these could not be seen by Case. Seeley mentioned the 

 occurrence of mucous grooves on the skull of Pareiasaurus, 

 but this has been questioned. So far as we are aware, these 

 are the only mentioned cases of anything resembling the 

 grooves described by Williston. The only notable differences 

 from the skull of Diadectes phaseolinus, the best known, are : 



1. There are no pits on the surface of the supraoccipital bone. 



2. The pits on the surface of the temporal region are very 

 obscure and cannot be certainly distinguished from the deep 

 interspaces of the rugosities. 



3. There are small pits on the surface of the prosquamosal 

 bones just anterior to the upper anterior border of the quad- 

 rate. 



4. The jugal descends to the lower edge of the quadrate. 

 These differences are certainly not of generic value. 



The nares are far anterior and in the crushed condition of 

 the specimen appear to look upward ; this is, however, an exag- 

 geration of the natural condition, in which the nares were 

 inclined somewhat inward and forward and looked almost 

 directly outward. The nasal canal is inclined inward and down- 

 ward and opens on the sides of the palatines and prevomers 

 (vomers) at the posterior edge of the premaxiliaries, a little 

 posterior to the anterior opening. 



The orbits are elongate oval in outline and inclined slightly 

 inward at the upper edge. 



The parietal foramen is, as in all the Diadectidae, 'enor- 

 mous'. These are the only openings in the skull except the 

 otic. 



The premaxiliaries are short and very heavy. Each one 

 carries four strong incisor teeth (not two as described by Marsh) 

 very prominent and protuberant ; this is most evident in the 

 median ones; the inclination becomes less in the outer teeth. 

 The inner surface of the crown is beveled by a flat surface 

 forming a strong chisel-like cutting edge. The surface of the 

 crown is smooth but the roots are marked by deep striations. 

 An isolated incisor tooth from another specimen has an imper- 

 fect root 22 mm long with the crown 17'5 mm long. There can 

 remain no question of the true thecodonty of the teeth. 



The maxillaries have the alveolar portion greatly swollen 



