X.] MAN. 131 , 



shallow. The cribriform plate which closes it in front, in- 

 stead of being vertical, as in the Dog, is horizontal, and 

 almost in the same line with the basicranial axis. It is 

 bounded in the median line, and separated from the cor- 

 responding fossa of the other side by the prominent crista 

 galli of the mesethmoid. The middle fossa is, as before 

 said, of comparatively enormous extent ; it is bounded pos- 

 teriorly by the tentorial ridge, having the same relations to 

 bones as in the Dog, but lying more horizontally and being 

 far less prominent, having no osseous shelf-like inward exten- 

 sion. This fossa is distinctly divided into an anterior and 

 posterior portion, by the strongly projecting hinder ridge of 

 the orbitosphenoid. The floor of the anterior portion is 

 arched in consequence of the inward projection of the roof 

 of the orbit, while the floor of the posterior, or " temporal 

 fossa," is deeply concave. The cerebellar fossa is of mode- 

 rate size, and Hes entirely underneath the hinder part of 

 the cerebral fossa. 



The " sella turcica," or depression in the basisphenoid for 

 the lodgment of the pituitary body of the brain, is bounded 

 posteriorly by an elevated transverse ridge, the corners of 

 which are called the " posterior clinoid processes." Cor- 

 responding processes projecting backwards from the orbito- 

 sphenoids are called " anterior clinoid processes." 



The foramina in the base of the skull scarcely differ from 

 those of the Dog. i. The olfactory has been already 

 described. 2. The optic is a large round hole close to the 

 inner and posterior part of the orbitosphenoid, 3. The 

 sphenoidal fissure is larger than in the Dog, and produced 

 externally into a long narrow slit. 4 and 5. The foramen 

 rotundum and the foramen ovale pierce the alisphenoid, one 

 near its anterior, the other near its posterior border. Close 

 behind the last-named is a small hole (" foramen spinosum "), 



K 2 



