582 Bulletin American Museum of Natural History. [Vol. XIX, 



Lunar. 

 The transverse surface of the radial facet is convex in this 

 form and the posterior extension of the same surface is 

 broadly expanded, while in M. rohustus it is nearly flat 

 transversely and contracted on the posterior surface. 



Digits of Manus. 

 The three phalanges of the middle digit are preserved, and 

 differ considerably from those of M. rohustus. The claw 

 process of the ungual phalanx is somewhat deeper than wide, 

 of an ellipsoid outline. The under surface is not separated 

 from the sides by sharp ridges toward the distal end, as in 

 Mylodon, and it is only toward the base that these ridges are 

 shown. The middle phalanx resembles that of Mylodon, 

 though the proximal facet is much deeper. The proximal 

 phalanx is very much shorter than in M. rohustus; the 

 outer surface is twice the width of the inner surface and is 

 expanded on the lower outer side. The proximal articular 

 facet presents a deep concave channel for the articulation 

 of the trochlea of the metacarpal; on the inner side of this 

 channel, continuous with its inner edge, is a narrow, con- 

 cave articular surface. The outer surface of the trochlear 

 depression presents a sharp ridge. On the ventral surface 

 there is a sesamoid facet on each side of the trochlear depres- 

 sion, the outer being the larger. The distal articular facet 

 is a wide shallow channel, concave from side to side and con- 

 vex vertically. Below the distal articular surface there is 

 a rugose depression one fourth the height of the articular 

 surface. 



Measurements. 



Skull. 



mm. 



Length of m^ 29 



Width " " 15 



Length " m^ 26 



Width " " 23 



Length " m^ 23 



Width " " 25 



Length " m* 30 



Width " " 17 



