i4r 



THE SKULL. 



[chap. 



In the Howling Monkeys [Afycetes) the hinder or ascend- 

 ing portion of the ramus is remarkable for its extent, both 

 vertically and antero-posteriorly, corresponding to a certain 

 extent with the extraordiiiary development of the vocal 

 organs, which it partially covers and protects. 



The Siiniina are remarkable in never, or very rarely, 

 having an ossified stylohyal ; but on looking closely at the 

 base of the periotic, immediately to the anterior and inner 

 side of the stylomastoid foramen, a very small depression, 

 in which there is sometimes a minute ossified tympano-hyal, 

 can generally be seen. To this the ligament representing 

 the stylohyal is attached. 



In very few of the Old World Monkeys is there any 

 ossification in the anterior hyoid arch (see Fig. 50) ; but in 

 some Cercopitheci a short, bony, ceratohyal is found. This 

 occurs also in the American Monkeys (Fig. 51), with occa- 

 sionally the addition of a second piece (epihyal). 



The thyrohyals are always well-developed, long, narrow, 

 nearly straight, and somewhat flattened. 



Fig. 50. — Inferior surfa< e of hyoid bones 

 of Baboo'i {CynocepJiahis porcariits ■. 

 bh bai^ihyal ; tk thyrohyal. 



Fig. 51. — Inferior sui face of hyoid bones 

 of an American Monkey {Lagothri^: 

 Inunboldtii). th thyrohyal ; ck cerato- 

 hyal ; eh epihyal. 



The basihyal varies much in form. In the anthropoid Apes 

 it is broad transversely; but in nearly all the other Monkeys 

 its antero-posterior extent exceeds its breadth, owing to a 



