532 ANATOMY OF VERTEBRATES. 



portions of skull than do those (Orang, Gorilla) of the higher 

 group. 



In the Black-faced Drill (^Cynocephalus porcarius, fig. 351) 



the facial much exceeds the 

 ^^^ ^^^ cranial part of the skull. The 



superoccipital is almost flat : 

 but, sloping upward and back- 

 ward, forms an acute angle with 

 the parietal, from which it is 

 divided by a strong ridge, where 

 the diploe is obliterated. The 

 mastoid is more developed than 

 skuu ,ci>noce,naius porcarius^. Lxix-. ^hc paroccipital promiuencc ; but 



both are low. The jugular fossa 

 is distinct from the precondyloid and carotid foramina ; outside the 

 latter is a short ' vaginal ' process. The petrosal bifurcates anteri- 

 orly into a ' eustachian ' and an ^ apical ' process: the latter under- 

 laps the base of the pterygoid process : the inner surface of the 

 petrosal is closely applied to the basisphenoid and basioccipital as 

 far as the ^ foramen jugulare : ' there is, thus, no ' foramen lacerum 

 basis cranii.' The squamosal is perforated near its middle by one 

 or two small foramina, but there are no ^ post-glenoid ' outlets of 

 the lateral sinuses. The foramen ovale is between the petrosal 

 and alisphenoid, and the nerve which it transmits pierces the base 

 of the broad ectopterygoid : the entopterygoid plate is compara- 

 tively small, but ends in a hamular process. The glenoid arti- 

 cular surface projects from the under part of the base of the 

 zygoma, and is slightly convex : it is defended by a postglenoid 

 process. The vomer divides the posterior nostrils, and there is a 

 venous sinus or foramen between its base and the presphenoid. 

 The coalesced nasals are prominent and gradually expand as they 

 advance forward : they unite with a small proportion of the pre- 

 maxillaries. The fossae between the nasals and maxillary tuber- 

 osities are short and Avide. The pterygoid fossae are large and 

 deep. The alisphenoid is separated by the squamosal from the 

 parietal. The upper angle of the mastoid is wedged between the 

 superoccipital and parietal. The limits of the interparietal may 

 be traced upon the inner surface of the calvarium. There is a 

 shallow cerebellar fossa above the meatus internus. The optic 

 foramina are approximated. The entry to the rhin en cephalic 

 fossa is much contracted by the bulging prominence of the roofs 

 of the orbits. 



In the Magot (Macacus Inuus, fig. 352) and other Macacques, 



