No. 434-] THE AMERICAN PELYCOSAURIA. 89 



extending horizontally forward. The vertical arm overlaps the 

 outer surface of the quadrate as described and meets the squa- 

 mosal, the horizontal arm joins the jugal and forms with it a 

 strong inferior bar. Seen from the rear it is evident that the 

 squamosal comes down as far as the lower limit 

 of the quadrate and appears on the outer surface 

 of that bone. The pterygoid comes well up on 

 the inner surface so that the quadrate is prac- 

 tically surrounded by bones and has relatively 

 small vertical extent. Figure 2. 



The facial portion of the skull is formed al- 

 most entirely by the maxillary which presents 

 some peculiarities. It is relatively long and the 

 alveolar edge is almost straight with hardly a 

 trace of the sharp downward convexity of the 

 specialized Pelycosauria. On the inner side of 

 the maxillary the lower edge is locally thickened 

 by the development of a sharp buttress which 

 accommodates the roots of the teeth ; near the 

 anterior end of the maxillary there is a single greatly enlarged 

 canine and the buttress is correspondingly enlarged but no where 

 near so much as in the most specialized forms of Dimetrodon, 

 instead there is a strong rib developed on the lower side of the 

 maxillary from the base of the root of the tooth to the top of the 

 maxillary bone. The root does not extend into the bone as far 

 as in Dimetrodon. This maxillary canine is rather more pos- 

 terior in position than in Dimetrodon, posterior to it are 19 

 counted teeth and alveoli, but a portion of the bone is covered 

 by a fragment of the lower jaw so that there were probably from 

 23 to 25 teeth ; anterior to the canine are four teeth and alveoli 

 in the maxillary. Where the maxillary meets the premaxillary 

 there is a shallow depression of considerable anten .-posterior 

 extent, but it is lined with teeth throughout so that it is but the 

 beginning of a diastema. 



The form of the premaxillary is quite simi 

 trodon, there is a vertical anterior process 

 anterior edge of the nares. There is but a single large 1 

 which is the first or inner one and posterior 

 much smaller. 



r to that of Dime- 

 Arhich forms the 



there ; 



