1884] 31 [Cope. 



phalanges of the posterior feet. The bones of the skull are mostly pre- 

 served, but in a dislocated condition. They serve to demonstrate some of 

 the characters of the genus and family. 



The quadrate bones of both sides are distinctly displayed. They are 

 rather short, and articulate above by squamosal suture with the squamosal 

 bones, which overlap them posteriorly, They narrow upwards, and are 

 deeply grooved on the anterior face below. Each edge of the groove is 

 produced forwards ; the external for a considerable distance as an acumi- 

 nate laminiform process, in the usual position of a quadratojugal bone. 

 The production of the internal edge is shorter, and its extremity is verti- 

 cally truncate. Its superior edge fits an incurvature of the superior edge 

 of the pterygoid bone, and its internal face is applied to the external face 

 of the latter. 



The pterygoid bone displays the subtriangular plate with dentigerous 

 edges, such as I have already described as present in the species of Dime- 

 trodon. In this species it is thinner and less massive than in any species 

 of that genus yet known. This specimen enables me to locate it more 

 precisely than heretofore. The pterygoids were probably placed much as 

 I have represented them to be, in the JSmpedias molaris Cope (Proceedings 

 American Philosoph. Society, vol. xix, p. 56, pi. v). They send inwards 

 a subtriangular plate from each side, which approach each other on the 

 median line without touching, and the adjacent edges are somewhat de- 

 curved. The posterior edges are deeply concave on each side of the mid- 

 dle line, and like the inferior edges, are dentigerous. The process for the 

 quadrate extends outwards and backwards, and is thickened on its poste- 

 rior edge, while its anterior edge, which is continued from the inferior edge 

 of the posterior border, becomes very thin. The anterior production for 

 the ectopterygoids extends outwards and forwards, leaving the anterior 

 edge of the dentigerous plates as the concave posterior border of the large 

 palatine foramina. The anterior production of the internal edge of the 

 plate becomes very thin, and is broken in the specimen without showing 

 articulation for the palatine. 



The squamosal extends both above and below its anteriorly directed 

 zygomatic portion. The superior extremity shows squamosal suture for 

 the parietal. 



The stapes is of large size. It consists of a stout rod terminating in a 

 double extremity, something like the double head of a rib. The shorter 

 head is expanded into a funnel shape. Near to it the shaft is perforated in 

 the longer diameter by a foramen. The extremity of the other head is 

 transversely truncate and is separated from the funnel by a deep notch. 

 On the outer side of the fundus of this notch, a foramen penetrates the 

 shaft obliquely and is continued into a canal which issues at the foramen 

 first described. The distal end is truncated by an irregular sutural sur- 

 face. In the specimen the bone lies behind the squamosal and quadrate 

 bones, the simple extremity of the rod near the posterior edge of the 

 quadrate. 



