o 



Mwmmalia. Quadrumana. 



maxillaries are distinct on the facial surface. The Orbits are 

 completely circumscribed by an osseous ring; but the temporal 

 and orbital fossa are seldom entirely separated, except in the 

 Catarrhina. The Glenoid cavity is usually less deep than in 

 Bimana, and is bounded posteriorly by a well-marked post- 

 glenoid ridge (exc. Cheir^mys). The Alveolar border of the upper 

 jaw never forms a regular curve ; and even when it approaches 

 that shape, has some of the alveoli protruding beyond the rest. 

 The Bami, of the lower jaw, are rounded oif at each end, both at 

 the symphysis and at the " angle/' The Basi-hjal is generally 

 expanded and excavated posteriorly ; and the Cerato-hyals developed 

 into processes, being very rarely represented by mere tubercles 

 [e.g. in Gorilla). The JVasals are generally flat. In the Mhmoid 

 the crista galli is very rudimentary (exc. Cercopithecus). The 

 Clinoid processes of the sella are generally sinall or rudimentary, 

 except in the Catarrhina. Yery commonly a division of the Lateral 

 Cerelral venous sinus excavates the base of the petrosal, to terminate 

 at the post-glenoid fossa. (? Catarrhina.) 



1. Catarrhina. In all Catarrliina the bony septiim bchvocn the orLital and 

 temporal fossa is complete. The nasals are flat, small, and generally coalesced. 

 In yoimg Apes ihe foramen may ?mm sometimes assumes a horizontal position. 

 The rami 'are generally coalesced early at the symphysis. There are seldom 

 any " post-glenoid " outlets of the lateral sinuses (exc. Hylobates.) The 

 tentorium is never ossified. The preclinoid and postclinoid processes are well 

 developed. 



2. Platyrrhina. The frontal suture is obliterated in all, and the single hone 

 thence resulting is triangular, with the apex extending back between the 

 parietals, in some capuchins (cebus) as far as the superoccipital, thus repeating 



a Piscine collocation of supra-cranial bones. In most of this group (exc. 

 Callithrix) the plate which divides the orbital from the temporal fossa, exhibits 

 a small unossified vacuity. The lachrymal foramen is within the orbit (cf. ii. 3), 

 and the orbital walls project considerably into the cranial cavity. The 

 mandibular rami of Mycetes are especially to be noted on account of the extra- 

 ordinary depth of their angular and ascending portions ; this development 

 relating to the protection and support of the still more extraordinarily developed 

 hyoidean and laryngeal apparatus. The Hyoid arch is reduced to the 

 basi- and thyro-hyals only ; but of these, the former is enormously developed 

 and expanded into a capacious sac, with thin walls, and a posterior opening 

 admitting a laryngeal pouch. In other Platyrrhina the cerato-hyals are 

 present, and the basi-hyal is slightly exQavated, forming in Hapale only a 

 convex plate. The lateral sinuses have " post-glenoid" outlets, Atele* 

 furnishes an example of ossification continued into one half of the tentorium. 



