348 Case and Wiliiston — Description of Reptilian Skulls. 



The edges of the two bones forming the keel were lined with 

 small conical teeth, now indicated by the bases. At the pos- 

 terior end there are four such teeth in 15 mm ; similar teeth can 

 be detected throughout the length of the keel. ~No small teeth 

 can be detected on the sides of the pterygoids adjoining the 

 keel, but this may be due to the condition of the bone or the 

 accidents of preparation ; the surface of the bone is partly 

 destroyed. 



The prevomers are hidden by the matrix except the lower 

 edge ; it seems probable, however, from the appearance of the 

 upper surface of the palate, revealed by the crushing of the 

 facial region, that the palatines had the same relation to the 

 prevomers as in Diadectes. 



The basisphenoid is similar to that of Diadectes but is very 

 much longer and there is no foramen in the median line. In 

 the deep pit anterior to the basisphenoid can be seen the pos- 

 terior end of a strong parasphenoid rostrum. The posterior end 

 of the basisphenoid is not entirely cleared but it is quite similar 

 in general form to that of Diadectes. 



The quadrate is inclined inward so that its outer surface looks 

 rather backward than outward. There is no indication of the 

 pit opposite the anterior edge of the quadrate. The inner edge 

 describes the same sharp curve as in Diadectes and there is 

 the same deep notch at the upper end of the otic opening. 

 The articular face is very much narrower than in Diadectes, 

 the anterior p sterior diameter being only 9'5 mm and the trans- 

 verse at least 24 mm - Diadectes lentus the same diameters 

 are I7 mm and 24 mm . Ivioreover the outer half of the articular 

 surface is nearly the same width as the inner ; in Diadectes 

 the outer is much wider than the inner. 



The genus evidently belongs in the family Diadectidce, but 

 may be distinguished by the following characters : 



1. The union of the pterygoids in the midline to form, 

 with the prevomers, a prominent keel. 



2. The absence of any interpterygoid space. 



3. The elongation of the basisphenoid and the absence of 

 a foramen in the median line. 



4. The inward inclination of the quadrates narrowing the 

 occipital region. 



The animal must have been similar in form and habits to 

 Diadectes. It has been customary to regard the members of 

 this family tfs herbivorous, but the strong, chisel-like incisor 

 teeth, the absence of any power of trituration in the unworn 

 maxillary teeth and the possibility of the use of the palatine 

 processes of the maxillaries as accessory agents of mastication 

 lead to the -ispicion that the animals were not exclusively if 

 at all herbi' ,rous, and that they may have included the less 

 well-protected invertebrates in their diet. 



