14 



MEMOIR ON THE in. 



from the weainng influence of running water; but they appear originally to have 

 been more unilbrmly convex than in the Bison, or they have not been so abruptly 

 bent about their middle. The inferior portion also is very much less inclined out- 

 wards from a level than in the latter. 



The occipital foramen is absolutely a little less in size than in the Bison, and 

 is almost one inch and a half in diameter. 



The base of the paramastoids is thick and pyramidal, and between these and the 

 condyles is a broad shallow concave surface not more than three fourths of an inch 

 deep from the level of the lowest part of the condyles, while in a corresponding 

 position in the Bison a fossa exists at least two inches in depth from the same 

 points of measurement. 



The basilar process is three and a half inches wide posteriorly, and is strongly 

 marked by the attachment of the anterior cervical muscles. The prominences 

 just in advance of the condyles are one and a half inches wide, and to their outer 

 side, about ten lines in advance of the condyles, is the foramen condyloideum. Just 

 anterior to the latter, and separated from it by a simple transverse ridge, is the 

 jugular foramen, and in advance of this is the os tympanica, not at all inflated, but 

 presenting an irregular crest continuous from the base of the paramastoid inwards 

 and forwards to the side of the basilar process, and there terminating in a short 

 compressed conoidal apophysis. Immediately internal to the latter is the foramen 

 lacerum, and from this the groove is continuous to the inner side of the pterygoid 

 processes, for accommodating the Eustachian tube. 



The stylal depression is a cylindrical pit half an inch deep and in diameter. 



The auditory process commences in a vaginal apophysis, continuous with the 

 OS tympanica, forms the anterior wall of the stylal depression, and has an 

 oblique position outwards, backwards, and upwards. Its anterior surface is con- 

 cave, and its lower margin ^Dresents a groove, passing outwards from the stylal 

 depression, bounded on each side by a ridge, the anterior of which is acute and con- 

 tinuous with the margin of the vaginal process. Between the paramastoids, stylal 

 pit, and auditory process is the stylo-mastoid foramen. 



The meatus auditorius externus is longitudinally oval, and is situated about 

 twenty lines above the level of the lowest part of the basilar process. 



The glenoid articulation is, in a trifling degree, less convex than in the Bison, is 

 about two and a half inches in breadth, and one and a half antero-posteriorly, and 

 is on a level with the upper part of the meatus auditorius externus. 



The post-glcnoid tubercle is compressed conoidal, with a slight twist, and is longer 

 than in the Bison. 



The glenoid foramen is circular, about two lines in diameter, and occupies a 

 position immediately outside of the post-glenoid tubercle. 



The root of the zygoma, at its outer margin, projects considerably external to the 

 position of the base of the horns. Its upper surface above the glenoid articulation 

 presents a large deep concavity, above which, posteriorly, are two large foramina. 



The space between the glenoid articulation and the root of the zygoma is much 

 narrower than in the Bison, and the foramen rotundum is less advanced, being on 

 a line with the anterior fiice of the post-glenoid tubercle. 



