NO. 2 A STUDY OF MENISCOTHERIUM — GAZIN 20, 



appear at a point just median to the foramen ovale. The anterior 

 portion of each wall is composed rather largely of the vertical or 

 ascending plate of the palatines, and a well-developed and widely 

 open pterygoid fossa extends anteriorly well into and dividing the 

 lower margin of these plates posteriorly. The pterygoid plate of 

 the alisphenoid, the principal element composing the outer wall of the 

 pterygoid fossa, is thicker and more sturdy than the pterygoid proper 

 forming the medial wall, and its ventrolateral^ directed lower margin 

 exhibits a hamularlike process, possibly better developed than the 

 hamular process of the pterygoid, although this is uncertain because 

 in no specimen at hand does the lower margin of the pterygoid appear 

 to be complete or undamaged. Immediately posterior to the ptery- 

 goid fossa, just above the point where the pterygoid and pterygoid 

 plate of the alisphenoid join, is the posterior opening of the ali- 

 sphenoid canal, lower and rather well in advance of the foramen 

 ovale. The alisphenoid canal is essentially within the lateral wall 

 of the mesopterygoid fossa opening at a distinctly ventral position on 

 its posterior margin. From its posterior extremity the course of the 

 canal, distinctly upward and forward to its junction with the foramen 

 rotundum, has been observed in damaged specimens. Posterior to 

 this junction a fair-size opening on the dorsomedial wall of the canal, 

 about midway in its length, has been observed in one specimen, but 

 the course of this foramen has not been determined. In all proba- 

 bility it enters the body of the basisphenoid. 



The foramen ovale, well removed from the alisphenoid canal in 

 Meniscotherium, is lateral to and may be slightly in advance of the 

 anterior margin of the foramen lacerum medium. Extending pos- 

 teriorward into the otic fossa from the medial margin of the foramen 

 ovale is a very feeble crest which would seem to define the path of 

 the eustachian tube. From the posterior margin of the foramen ovale, 

 however, there is a very prominent and anteroposteriorly elongate 

 process or crest, the styloid process of Cope, medial to and well 

 separated from the postglenoid process, which apparently consists 

 of laminae of both the alisphenoid and squamosal. Its position is 

 near or about that of the angular spine of the alisphenoid in man 

 which supports a portion of musculature of the soft palate and of the 

 tympanum. Nevertheless, I suspect that here it is homologous to 

 the prominence in this position in certain other mammals, such as the 

 oreodonts, where it forms a pedicle for support of the anterior 

 portion of the bulla. No tympanic bulla has been discovered during 

 preparation of any of the Meniscotherium cranial portions. It may 



