163 



walls. It extends so far backwards that it abuts against the 

 anterior half of the occipital condyles, and reaches forwards to a 

 point corresponding to about the middle of the zygomatic arch. 

 Its anterior third is formed by the alisphenoid, the middle third 

 by the tympanic, and, into the formation of the remainder, both 

 the mastoid portion of the periotic and of the exoccipital 

 appear to enter, but the latter cannot be, with certainty, defined 

 from the other elements of the occipital bone. 



In the anterior part of the orbito-temporal fossa, the lateral parts 

 of the frontal and the lachrymal project outwards and somewhat 

 backwards, forming a prominence, instead of a hollow, in the orbital 

 region, which has exceedingly thin walls. Behind this prominence, 

 and corresponding to about the junction of the anterior and middle 

 third of the orbito-temporal fossa, the skull is constricted by a 

 shallow groove passing downwards and backwards, corresponding 

 to that which usually marks out the division between the orbital 

 and temporal parts of the fossa. Behind this groove the cranium 

 bulges a little, and is then again constricted by a similar groove, 

 which runs downwards and a little forwards, nearly meeting the 

 other above the sphenoidal hssure. (PI. VI., and VII., fig. 1.) Behind 

 this again, the skull broadens very rapidly towards the posterior 

 root of the zygoma, at which point it is widest. Posteriorly the 

 contours converge till they meet the lateral edge of the occipital 

 plane. Sutures between the bones on the side of the skull, other 

 than those mentioned, cannot with certainty be distinguished. 



In a view of the inferior surface of the skull, almost the whole 

 extent of the foramen magnum is seen, which thus faces very 

 much downwards. Anteriorly, the basioccipital is completely 

 ankylosed with the basisphenoid, though the junction is well 

 defined by a transverse ridge. There are no paroccipital processes, 

 and the exoccipitals have been described as forming part of the 

 auditory bulla3. 



Besides the basisphenoid, parts of the presphenoid, pterygoids 

 and palate bones enter into the formation of the roof of the 

 mesopterygoid fossa, which is wide anteriorly, but much nar- 

 rowed behind. Its lateral walls are thin and lamelliform, curving 

 inwards at their inferior edges, and the pterygoids end in well- 

 marked, slender and backwardly-projecting hamular processes. 



The contour line of the hard palate, including the alveolar 

 borders, gives a markedly pyriform outline, being very wide oppos- 

 ite the middle of the molar series of teeth and tapering ante- 

 riorly. The bony palate has a straight posterior border, and its 

 surface is arched transversely; at its junction w4th the lateral sur- 

 faces of the face a sharp edge-like alveolar border is formed, wliich 

 abuts on the outer borders of the teeth. The junction between 



