208 
DES. A. CAETE AND A. MACALISTEE ON THE 
sented an oval aperture which transmitted the Eustachian tube inferiorly, and the tensor 
tympani muscle superiorly; the former passed into the upper part of the tympanic 
cavity, the latter hooked round a spur of bone which lay immediately external to the 
border of the former. On its inner surface the squamous bone was deeply excavated for 
the accommodation of the petrous element, and its cerebral surface was smooth and con- 
cave * 
The alisphenoid or pterygoid bone exhibited three aspects. First, an inferior or pte- 
rygoid, which consisted of two osseous plates, external and internal, separated by a deep 
ovoid cavity, the pterygoid fossa ; the external plate was united with the petrous or peri- 
otic and mastoid bones by suture, the latter of which overlapped it ; and the anterior 
part of the former was received into a pyramidal depression formed by the meeting of 
the mastoid and pterygoid bones. The internal plate was thick behind, extended further 
back than the external, and met the lateral ridge on the basioccipital ; this plate formed 
the inner boundary of the posterior nares, and was convex from before backwards on 
its inner aspect ; above and internally it met the outer edge of the vomer, into a groove 
in which it sent a sharp vaginal ridge forming a schindylesis articulation. The ptery- 
goid plates united below to form a round blunt hamularf process, about an inch and 
a half in length, which was directed backwards and slightly outwards. In front of the 
pterygoid bone a series of lamellae projected, which interlocked with a similar series of 
plates on the palate-bone. The second or temporal surface was somewhat triangular in 
outline and rounded along its upper edge ; this surface was concave outwards, it arti- 
culated with the parietal in front, with the mastoid posteriorly and above, and with 
the temporal aspect of the basisphenoid anteriorly. The inner or cerebral surface 
was smooth, and appeared concave in front, where it formed the floor of the sphenoid 
fissure. 
The basisphenoid presented on its upper or cerebral surface a central hollow or 
groove, sella turcica, in which appeared four small foramina ; this fossa was bounded in 
front by a very small roundish eminence, the rudimentary middle clinoid, or, more cor- 
rectly, olivary process ; and posteriorly by a similarly diminutive posterior clinoid ; the 
posterior edge of the bone presented an elevated transverse ridge, which marked its 
union with the basioccipital bone. Midway between the external edge and the sella 
turcica, on each side, a foramen was seen, from which a narrow canal was traceable 
downwards, backwards, and outwards, and opened on a small triangular surface of this 
bone externally between the basioccipital and the alisphenoid. This vascular channel 
represents the canal of Vesalius. In front of the sella turcica a transverse suture was 
situated, which separated the anterior or presphenoid element from the basisphenoid. 
Still more anteriorly the former was grooved for the optic nerves and commissure ; as 
this groove extended outwards and forwards on each side, it was formed into a foramen 
by a thin scale of bone which completed it superiorly and posteriorly, and appeared to 
* For a description of the petrous bone, vide “ The Organ of Hearing.” 
t Eschricht and Eeinhardt mention that this process is scarcely distinguishable, which description does not 
accord with the present specimen. 
