VIII.] PRIMATES. 91 



of curvature on the external surface of the rib is called the 

 angle. 



Each vertebral rib has a main centre of ossification and 

 two epiphyses, one for the head, and (except in the last 

 two), one for the tubercle. 



The sternal ribs generally remain cartilaginous throughout 

 life, being only partially ossified by endostosis in old age 

 or under abnormal conditions. They are not distinctly 

 separated from the vertebral ribs except by their difference 

 of structure ; but synovial joints are (except in the first) 

 interposed between their inferior extremities and the 

 sternum. 



Among the higher Simiina the ribs do not differ very 

 notably from those of Man, except in number ; but in the 

 lower forms, and especially in the Lemurina, they more 

 resemble those of the Carnivora. Among the Old World 

 Monkeys, the number varies from 11 to 13 pairs. The 

 Gorilla and Chimpanzee {Troglodytes) have 13, and the 

 Orang {Siniia) 12. In the American Monkeys there are 

 from 12 to 15 pairs; in the Lemurs from 12 to 16 pairs. 



In the most typical forms of Carnivora, the vertebral 

 ribs are comparatively slender, subcylindrical, and little 

 curved. The most anterior especially are short and straight, 

 the thorax being thus more compressed in front than it is in 

 Man and the higher Primates. The sternal ribs (see Fig. 

 33> P- 1S\ ^i"^ loiig? slender, have a feeble granular ossifica- 

 tion, and are not otherwise segmented ofli" from the vertebral 

 ribs. In all the Felidce and Cmiidcc. there are 13 pairs, in 

 the VivejiidcB 13 or 14, in the Hycenidce 14 or 15, in the 

 MiistelidcE 14 to 16, in the Frocyonidce 14, in the Ursidce 14 

 or 15, in the Piimipedia 14 or 15. 



In the Ungulata, the ribs are generally niore or less 

 flattened and broad, notably so in the Ox and Camel, and 



