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with an oblique base and an obtuse apex. The distal articular surface is 

 of a triangular form, with the angles rounded off, and is divided into two 

 parts ; the larger portion being placed on the tibial half of the base of 

 the bone, and applied to the outer facet of the anterior cuboidal articu- 

 lation ; the remaining portion encroaching upon the tibial side of the 

 bone, and abutting upon the outer articular surface of the adjoining me- 

 tatarsal. 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, was doubtless inserted and expanded over 

 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 trans- 

 ferred the superincumbent weight of the massive hinder parts of the 

 Mylodon to the ground. The proximal articulations of the fifth meta- 

 tarsal are so placed as to make it the key-stone or centre upon which 

 almost the whole weight of the foot is concentrated. Thus the pressure 

 sustained by the astragalus is transmitted in part by the naviculare, ex- 

 ternal cuneiform, and outer production of the base of the middle meta- 

 tarsus upon the side of the fourth metatarsus which rests by the opposite 

 side, in the usual inverted position of the foot upon the fifth metatarsal. 

 Another part of the weight of the astragalus is transmitted by the cuboides, 

 partly through the medium of the fourth upon the fifth metatarsal, partly 

 directly to that bone. A third portion of the weight sustained by the astra- 

 galus is transmitted to the last metatarsal through the calcaneum and os 

 cuboides. Sufficient need, therefore, for the surpassing strength and 

 size of the fifth metatarsal, since it had to share with the calcaneum, but in 

 a greater degree, in the support of the massive hinder parts of the 



