121 



The internal* of the two cuneiform bones is about half the size of the external 

 one, and of nearly the same antero-posterior diameter, but more compressed late- 

 rally, and of somewhat less depth : its convex base is uppermost ; its obtuse apex 

 downwards : the inner and outer sides are nearly fiat, rough, without trace of 

 smooth articular surface, which is limited to the anterior and posterior extremi- 

 ties of the bone. The posterior surface is elliptical, slightly concave, adapted 

 to the distinct circumscribed articular surface on the naviculare : the anterior 

 articular surface is nearly circular, and very slightly convex. There is no ar- 

 ticular surface upon the tibial or inner side of this cuneiform bone, nor any indi- 

 cation of a third or internal cuneiform on the os naviculare ; from which it is 

 to be concluded that the internal cuneiform bone and first toe, or hallux, were 

 altogether wanting in the Mylodon, and that the mutilation by which its hind- 

 foot is reduced to the tetradactyle type has commenced, according to the or- 

 dinary law, from the inner side. 



The toe articulated witli the foregoing cuneiform bone is the smallest of the 

 series, and consists of three phalanges and a metatarsal bone. The metatarsal! 

 is a moderately long, subcompressed bone, having its proximal end obliquely 

 truncated, and supporting a circular and nearly flat surface, below which there 

 is a rough tuberosity. A narrow vertical channel with a large perforation in the 

 middle, and with a convexity before and behind, chai'acterizes the outer side of 

 this bone ; its inner side is rough and similarly unequal : on neither side is there 

 the least trace of an articulation with an adjoining metatarsal. The distal end 

 presents a simple ovate articular convexity, with the small end upwards. 



The proximal phalanx is wanting in both feet ; but the large sesamoid bone s, 

 part of the surface of which adapts itself to the inferior facet of the distal 

 articulation of the metatarsal, indicates the former existence of such phalanx, as 

 does likewise the size and form of the proximal surface of the second phalanx : 

 it is, therefore, introduced of its probable size, in the figure, at m 2, 1. 



The second phalanx {m 2, 2), though small, is longer in proportion to its 

 breadth than in the great adjoining toe : it is slightly compressed, like the meta- 

 tarsal bone : the proximal surface is moderately and uniformly concave, of a 

 vertically oval form, turned slightly inwards, and with the larger end termi- 



* Plates XXI. and XXII./. 



t Plates XXI. and XXII. m, 2. The articulator has separated, in the foot here figured, the inner 

 toe a little too far from the adjoining or third toe. 



Q 



