THE SKELETON IN MAMMALIA. THIGH AND SHIN. 519 



In the UNGULATA VERA the femur is noticeable for the size 

 of the great trochanter (fig. 109, 2) ; there is no definitely 

 constricted neck separating the head from the rest of the 

 bone, and the lesser trochanter (fig. 109, 3) is not very promi- 

 nent. All Perissodactyles except the Chalicotheriidae show 

 a strongly marked third trochanter, but this is absent in all 

 known Artiodactyles. The development of the fibula in general 

 corresponds to that of the ulna. In Rhinoceros, Jlfacrauchenia, 

 Tapirus and the Suina it is distinct and fairly well developed ; 

 in the Tragulina on the other hand it is vestigial, being reduced 

 to the proximal end only. In the Rumiriantia and Tylopoda 

 also, it is much reduced forming merely a small bone attached 

 to the distal end of the tibia, sometimes as in the Red deer 

 a slender vestige of the proximal end also is preserved quite 

 detached from the distal portion ; in the Horse this proximal 

 portion is all that there is found of the fibula. The progressive 

 diminution of the fibula can be well seen in the series of forms 

 that are regarded as the ancestors of the Horse. The patella 

 of the Ungulata vera is well ossified, but fabellae 1 are not 

 usually found. 



SUBUNGULATA. Of the Toxodontia, Toxodon has no third 

 trochanter while Typotherium and Astrapotherium have one. 

 In the Condylarthra the femur has well-marked lesser and 

 third trochanters, and the fibula and patella are well developed. 

 In the Hyracoidea there is a slight ridge on the femur in the 

 place of the third trochanter, the fibula is complete, but is 

 generally fused to the tibia at its proximal end. 



Of the Amblypoda, Coryphodon has a third trochanter, but 

 Uintatherium has none ; in this respect, in the vertical position 

 and general appearance (fig. 108) of the limb, and in the 

 articulation of the fibula with the calcaneum, the leg of 

 Uintatherium closely approaches that of the Proboscidea. 



In the Proboscidea the femur is very long and straight, 



1 See p. 412. 



