1 4 2 



THE SKULL. 



[chat 



In the Howling Monkeys (Mycetcs) 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 extraordinary development of the vocal 

 organs, which it partially covers and protects. 



The Simiina 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 surface of hyoid bones 

 of Baboon {Cynocephahis porcarins,. 

 bh basihyal ; tk thyrohyal. 



Fig. 51. — Inferior sui face of hyoid bones 

 of an American Monkey (Laqothrix 

 humboldtii). th thyrohyal ; ch 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 j 

 its anteroposterior extent exceeds its breadth, owing to a 



