530 



ANATOMY OF VERTEBRATES. 



most Platymiines.^ The petrosal has a deep cerebellar depres- 

 sion. The postclinoid plate is more developed, the rhinencephalic 

 fossa is smaller, and the orbital walls project more into the cranial 

 cavity than in the Strepsirrhines. The lacrymal is not extended 

 upon the face, and the foramen is within the orbit. 



In Callitiirix sciureus the orbits do not communicate with the 

 temporal fossae. There are no paroccipitals, and only a feeble 

 mastoid ridge. The petrosals are slightly swollen at the basis 

 cranii. The parietals articulate mth the malars. There is a 

 vacuity in the interorbital septum. 



In Cebus, also, there are neither paroccipitals nor mastoids, and 

 the petrotympanics form slightly swollen convexities. Besides 



the postglenoid venous foramen, 

 there is a second at the end of 

 the squamosal suture. The fora- 

 men ovale is between the petro- 

 sal and alisphenoid. The super- 

 occipital plate has two large 

 depressions, as in Callitiirix. 

 The orbital plate of the malar 

 shoAvs a small hole near its junc- 

 tion with the alisphenoid.^ The 

 basi-hyal is excavated behind; 

 not so in Callitiirix : the anterior cornua are long, and formed by 

 epi- and cerato-hyals ; the thyro-hyals are broader, not longer. 



In the Spider Monkeys {Ateles) the paroccipitals and mastoids 

 form rough tubercles. There is the same venous foramen as in 

 Cehiis, formed by the meeting of two converging sinuses between 

 the squamosal and alisphenoid. Ossification has extended into 

 one half of the tentorium. The cerebellar fossa in the petrosal is 

 of great depth. The foramen ovale is formed by the petrosal and 

 alisphenoid. The vomer extends to the posterior nares. The 

 incisive foramen is large and single. 



The symphysis of the lower jaw is completely anchylosed, and 

 the angle of the jaw rounded oif, as in most Platyrrhines. The 

 condyles and small coronoid processes are of equal height : in 

 Marmosets the coronoid is higher, and in Hapale Jacchus the 

 mandibular angle is slightly produced. The basi-hyal is a convex 

 plate : the cerato-hyals are shorter than in Cebus : the thyro- 

 hyals are longer. 



' CIV. pi, vi. {Cebus, Douroucouli, Cliamek.) 



2 These relics of the orbito-tcmporal \ acuity Avere first noticed as such by Prof. 

 Filippi. 



Cnpurin (Cebnn Apella). LXix- 



