32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



edly closer is the glenoid surface for the lower jaw articulation. 

 This articular surface though slightly concave transversely is not 

 nearly so much so as in M eniscotherium, and its long axis is not 

 nearly so oblique. There is a well-developed postglenoid process 

 posteromedial to the center of the glenoid surface, and immediately 

 posterointernal to the process is a large postglenoid foramen with 

 its aperture entirely surrounded by the squamosal. The broad arch 

 of the squamosal over the external auditory meatus extends pos- 

 teriorly down the anterior surface of the moderately developed mas- 

 toid process, and the relatively greater ventral exposure of the mastoid 

 bone than in M eniscotherium causes the position of the audital tube 

 to be relatively farther forward from the condyles and more widely 

 separated from the paroccipital process. The paroccipital process 

 is not complete in any specimen at hand, but its root suggests that 

 it was fairly long and slender, although probably not so elongate as 

 in M eniscotherium. The condylar or hypoglossal foramen is located 

 decidedly medial and somewhat posterior to the paroccipital process, 

 close to and partially concealed by the posteroventral margin of the 

 condyle. 



Periotic. — Ventrally the petrosal of M eniscotherium presents an 

 almondlike oval to nearly triangular shape with its broad surface 

 facing anterolateral^ and ventrally, and its long axis extending anter- 

 omedially. Posterior to the promontorium the transversely elongate 

 fenestra rotunda faces downward and outward as well as slightly 

 backward, and anterodorsal to it the smaller fenestra ovalis faces 

 almost directly outward. On the ventrolateral surface of the petrosal 

 there can be distinguished a sinuous trace or broad groove from the 

 medial margin of the fenestra rotunda, adjacent to the foramen 

 lacerum posterius forward around the medial portion of the promon- 

 torium, then anteromedially to the apex of the petrosal. There would 

 appear to be a branch extending over the anterior portion of the 

 promontorium to the fenestra ovalis. One is tempted to interpret 

 this as the position of the internal carotid and its stapedial branch ; 

 however, I am inclined to consider the course of the internal carotid 

 as more medial with respect to the petrosal, as there is a broad groove 

 in the basioccipital that faces ventrally in its hinder part, medially 

 adjacent to the posteromedial angle of the petrosal, where the latter 

 solidly abuts the basioccipital. Forward, this groove turns outward 

 along the lateral margin of the basioccipital and adjacent to the 

 ventromedial margin of the petrosal to near the anterior extent of the 

 basioccipital and the apex of the petrosal where the groove opens 



