SKELETON OF QUADRUMANA. 



133 



general characters are those 



352 



Skull of Macacus Inuus 



with a general reduction of the size of the animal, the jaws are 

 concomitantly reduced, so that the cranial cavity forms one half 

 of the leno-th of the skull. The 

 noted in the Drill. In Ma- 

 cacus nemestrinus, a process of 

 styliform shape is developed 

 from the lower end of each 

 mastoid. The posterior clinoid 

 plate is largely developed and 

 is perforated. The cerebellar 

 fossa is moderately deep ; the 

 foramen ovale is between the 

 alisphenoid and petrosal. The 

 entry to the rhinencephalic 

 fossa is contracted by a pair of lateral processes. 



In the still smaller Monkeys {Cercoplthecus, fig. 353) the 

 cranial cavity forms a larger portion of the skull. In C. ruber, 

 the alisphenoid joins the parietal on the left side, not on the right. 

 In all the premaxillaries rise high between the maxillaries and 

 nasals : the interior of the cranium shows the cerebellar pit of the 

 petrosal, and the well-developed crista galli dividing the deep 

 rhinencephalic fossa. The postglenoid process is pointed, and in 

 some ( Cere, albogularis) the mastoid also : 

 the entocarotids pierce the petrosals. The 

 Doucs (^Sernnopithecus) have a similar pro- 

 portion of cranial cavity : in which the 

 cerebellar fossa of the petrosal is both large 

 and deep. The entry to the rhinencephalic 

 fossa is constricted by the approximation of 

 its lateral margins, which almost touch at 

 the middle. The foramen ovale is between 



the petrosal and the alisi)henoid. The tympanic air-cells extend 

 into the mastoid and squamosal. 

 The bony septum between the 

 orbital and temporal fossae is 

 entire in all Catarrhines. 



In the Gibbons (^Hijlohates, 

 fig. 354) the jaws are more 

 shortened, the cranium more ex- 

 panded. The alisphenoid is per- 

 forated by the foramen ovale, and 

 joins the parietal. The premax- 

 illaries do not reach the nasals. Sia.naag (Uulohates syndacUjlm). LXIX-, 



353 



Skull of Monkey {Ceropithecus 

 ruber). 



354 



