FREE APPENDAGES MAMMALS 3OI 



in the living genera, but Halithcrium has a vestigial femur articulated in a 

 distinct acetabulum. 



Primates have the appendages more primitive than in most mammals. 

 The femur has the entepicondylar foramen in Lemuroids and many new world 

 monkeys, none in the old world species. The tuberosities are httle developed, 

 but the olecranon fossa is deep in the monkeys of the eastern hemisphere. 

 Radius and ulna are separate and capable of extensive rotation, especially in the 

 higher genera. Radiale and intermedium are distinct, as is the centrale in most 

 species; in some (gorilla, chimpanzee and some lemurs) it is fused with the rad- 

 iale. A radial sesamoid is common and the pisiforme is long in the higher genera. 

 The carpus articulates with both forearm bones, except in Anthropoids and man. 

 The five digits are very variable in form and size in lemurs, in correlation with 

 their arboreal habits. In all Primates the thumb, and in most species, the 

 great toe are opposible to the other digits. The poUex is always short. The 

 femur has a small trochanter except in apes and monkeys. The humerus has a 

 small neck between shaft and the hemispherical head. Tibia and fibula are 

 separate and there is a slight rotation of the crural bones. In lemurs calcaneus 

 and centrale are long, especially in Tarsius (fig. 324). Of the five digits the 

 hallux is short and the fourth is the longest in lemurs. 



Here may be mentioned, to complete the list of vertebrate bones, the os 

 priapi (penis bone), an ossification arising in the connective tissue of the corpus 

 spongiosum of the penis. It occurs in a few Insectivores and in many rodents. 

 Carnivores and bats. Sometimes it is a simple rod; it is bent in Procyonidae, 

 grooved in Canidae (the urethra Ues in the groove) and forked in bats. 



