v.] SKELETON OF LOWER LIMB. 197 



The head of the femur is almost always rounded ; rarely 

 (as e.g. in the Crocodile) it is transversely extended, some- 

 what like that of the humerus in Birds. 



The greater (peroneal) and lesser (tibial) trochanters are 

 very constant structures, one or both appearing in a more or 

 less developed condition down to the lowest Batrachians. 



The great trochanter may be more prominent than in man. 

 This is the case, e.g., in Ungulates. It may, on the contrary, 

 be comparatively insignificant, as in the Great Ant-eater and 

 Elephant ; or absent, as in the Lizard Gramniatophora. 



The lesser trochanter may be about as salient as the 

 greater one, as in the Ornithorhynchus ; or much more so, as 

 in Uromastix, Lciocephalus, and Cyclodus; it may be all 

 but absent, as in the Elephant, or quite so, as in Birds. 



The two trochanters may be equally developed, one on each 

 side of a very short neck, as in Bats. 



The two trochanters may be fused into one, as in Testudo. 



In addition to the two trochanters, the slight ridge which 

 serves in man for the insertion of the gluteus maximus 

 muscle may be drawn out into a great prominence termed 

 a "third trochanter." This is the case, e.g., in the Horse, 

 Rhinoceros, Hare, and Armadillos. 



This third trochanter may be represented by a prominent 

 ridge running along the whole outer side of the shaft, as in 

 the Great Ant-eater. 



The head of the femur, instead of being directed inwards, 

 may project forwards over the exterior surface of the bone, 

 as in Tcstndo and the Bats. 



The pit for the ligamentum teres, though present in Birds, 

 may be quite absent in members of man's own class, e.g. in 

 Seals, Elephants, Sloths, and others. This depression, appa- 

 rently so important, may be present or absent in different 

 individuals of the same species, as in the Orang-Outan and 

 Gorilla. 



The lower end of the femur may be more, or less, expanded 

 relatively than in man, and this both transversely and antero- 

 posteriorly. 



Thus the latter dimension is greatly in excess in the Rumi- 

 nants ; the transverse dimension in the Seals and Ornitho- 

 ihynchus. 



Instead of the inner condyle descending the more, it may 

 be the outer one that does so, as is the case in Birds. 



The depression in front between the condyles " rotnlar 

 surface" (serving in man to lodge the patella) may be 



