138 E. B. BRANSON 



is not entirely convincing. The presphenoid is perfectly preserved 

 in one specimen in Walker Geological Museum but is lost in all 

 others examined. It is slender and extends about half the distance 

 from the basisphenoid to the anterior end of the skull. The sutures 

 between the vomers and palatines are not evident in any of the 

 specimens studied. 



In the specimen shown in Figs. 1 and 2, which is probably Parioti- 

 chus aguti Cope, though it has only two teeth on the premaxillaries, 

 the teeth on the maxillae are in one row to behind the fifth where a 

 second row begins inside the first, and behind this two other rather 

 indistinctly defined rows appear. Nearly all of the teeth are sub- 

 circular in cross-section near the base, but some of the posterior 

 ones are more or less compressed laterally. 



The distinction between Pariotichus and Labidosaurus made 

 by Cope, that the latter had the teeth of the maxillae in one row, 

 breaks down in the Walker Geological Museum specimens. In two 

 specimens examined during the present investigation a second row 

 of teeth is evident and in other specimens the preservation is not 

 such as to show whether there is more than one row. 



Mandible. — The dentary makes up the outer part of the anterior 

 half of the mandible. Just behind the dentary there is a short 

 coronoid which occupies about one-third of the width of the jaw 

 and sends upward a very large coronoid process almost equal in 

 width to the rest of the mandible. Behind the coronoid the angular 

 makes up most of the outer part of the posterior half of the jaw, 

 and also sends forward a slender process between the dentary 

 and the splenial, which reaches almost to the tip of the mandible. 

 Above the angular and separated from it by a suture that runs 

 diagonally across the jaw and passes to the posterior inferior corner, 

 there seems to be a surangular. The splenial is not well preserved 

 in any specimen observed and all that can be detei mined is that it 

 is a broad flat bone on the inside of the jaw. The articular is imper- 

 fect in all of the specimens, but in a perfect specimen of a closely 

 allied form, found completely separated from the other bones of 

 the jaw, it is heavy at the posterior end and sends a long slender 

 process forward. 



