704 PRIM A TES 



reduced to five in the Mandrill (Cynocepliahis maimon). In Macacus 

 and Uacaria the shortness of the tail is attained by the small 

 size of the vertebrae themselves, the number of which may be 

 from fifteen to seventeen. Other forms usually have from twenty 

 to thirty -three caudals, the latter number occurring in Ateles 

 (Fig. 335), where the tail is relatively the longest. The tail is, 

 however, absolutely longest in Semnopithecus, Colobus, and their 

 allies, the length being partly due to the size of the component 

 vertebrae. Chevron bones are present in all forms having a distinct 

 tail ; and, together with other processes for muscular attachment, 

 attain their greatest development in A teles. 



The vertebral processes known as metapophyses and anapophyses, 

 which are generally inconspicuous in Man, and are but small in the 

 Simiidce, attain a large development in the lower forms. The 

 metapophyses generally commence in the eighth or ninth dorsal, 

 and continue to the anterior caudals, where they gradually merge 

 in the prezygapophyses. The anapophyses, which are most de- 

 veloped in the Cebidce, project outwards and backwards from one 

 vertebra to embrace the prezygapophyses of the succeeding one. 

 They occur generally in the same region as the metapophyses, but 

 usually cease at the penultimate lumbar, although in some cases 

 they can be traced on to the posterior cervicals and anterior 

 caudals, in the latter region passing into the transverse processes. 



In most Apes the sternum is narrow, and consists of a more or 

 less enlarged manubrium, followed by a chain of subequal and 

 antero-posteriorly elongated bones, from three to six in number. In 

 the Simiidce alone is there a broad sternum, or one consisting of a 

 manubrium, followed by a single bone only, as in Hylobates. The 

 Orang presents a peculiarity, in that the sternum long remains 

 made up of ossifications arranged in pairs, side by side, successively. 

 The true ribs are seven in number on each side in the highest 

 forms, but in Hylobates there are sometimes eight. In Ateles there 

 are sometimes nine pairs. In Hapale the number varies from six 

 to eight, and it is seven or eight in the other genera. The angles 

 of the ribs are never so marked as in Man ; although most marked 

 in Hylobates. Pithecia is distinguished by the greater relative 

 breadth of the ribs. In no Ape is the thorax half as broad again 

 as it is deep from back to breast ; but in the Simiidce its transverse 

 diameter exceeds its depth by from about one-fourth to a little 

 under one-third of the latter. In Ateles, and sometimes in Mycetes, 

 the thorax is wider than deep, but in all the rest it is deeper than 

 wide. 



In regard to the appendicular skeleton it may be observed that 

 the Gorilla and Orang make the nearest approach to Man in the 

 form of the scapula; and that the supraspinous fossa of this bone is 

 largest in Gorilla and Mycetes, being remarkably small in Simla. 



