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metatarsal. A slight concavity divides the basal articular surface from the large 

 rough protuberance, by which the bone is prolonged backwards and outwards 

 towards the os calcis. The strong tendon which traverses the outer groove of 

 the calcaneum had, doubtless, an expanded insertion into this protuberance and 

 the rough margin continued from it along the outer side of the metatarsal bone. 

 The upper surface of the bone is concave, with small elevations and vascular 

 foramina ; near the distal end the elevations assume the size of, or blend into a 

 rough protuberance : the short inner side of the bone is convex : the under- 

 side concave, divided by a rough ridge from the inner side. The signs of the 

 great pressure to which the outer rugged surface of this bone has been subject 

 are too obvious to be mistaken, and the position of the articulation of the foot 

 with the leg shows this to have been the surface which mainly transferred the 

 superincumbent weight of the massive hinder parts of the animal to the ground. 

 The proximal articulations of the fifth metatarsal are so placed as to make it 

 the focus or centre upon which almost the whole weight of the foot is concen- 

 trated. The distal end of the same bone is bevelled off almost to an edge, set 

 vertically ; on the outer side of which there is a small verticallj- elliptic and slightly 

 convex articular surface ; on the inner side and above there is a rugged protu- 

 berance and ridge ; below there are two oblique surfaces for sesamoid bones. 



The proximal phalanx is a diminutive shapeless rough bone, with the proxi- 

 mal surface adapted to the foregoing convexity. A very small and nearly flat 

 distal surface indicates the existence of some still more abortive representative 

 of a second, and doubtless terminal phalanx. 



The shape and superficial markings of the bones leave no doubt that the cur- 

 tailed and, as it were, amputated extremities of the two outer toes were sunk in a 

 hoof-like modification of the integument of the corresponding portion of the foot. 



Comparison of the Bones of the Posterior Extremity. 



In surveying successively the forms of the femora of the larger Mammalian 

 quadrupeds, we find in some of the great Pachyderms alone the shaft of the 

 femur flattened from before backwards, and thereby approaching to its charac- 

 teristic modification in the Mylodon. But in the Elephants and Mastodons the 

 length of the femur so far exceeds its breadth, that, strong as these bones are 



