ITS ANCESTORS AND RELATIONS 



25 



rest from its extremely primitive condition, each bone of 

 the second row standing directly beneath, and articulat- 

 ing almost entirely and only with, the corresponding 

 bone of the first row. 



The five digits, with their typical number of phalan- 

 ges, are completely developed, the third being the long- 

 est and strongest. The terminal or ungual phalanges 

 are expanded, flattened, and rather spatulate, and evi- 

 dently bore hoofs rather than claws. Each digit has a 

 metacarpal bone and three phalanges, except the first 

 or poll ex (corresponding to the thumb of man), which 

 has but two. 



In the hind leg, the femur or thigh-bone shows con- 

 siderable evidence of the presence of that projecting 

 ridge on the outside, known as the third trochanter, 

 found in all Perissodactyles, but in none of the Artio- 

 dactyle section. The two bones of the lower leg, the 

 tibia and fibula, are distinct and complete. 



In the ankle or tarsus the cuboid articulates with the 

 calcaneum only. The astragalus presents a uniformly 

 convex distal articular surface, as in Carnivora, but it 

 has a trochlea or pulley-like proximal end, which the 

 still more generalised Periptychus has not. The toes are 

 five in number, much resembling those of the fore-foot. 

 The animal was apparently not plantigrade, or walking 

 with the whole of the sole of the foot, from the heel or 

 hock to the toes, on the ground, as the bears do, nor did 



