336 A NEW MYLODON. 



expands to an extreme width of 117 mm., with a median jidge which begins at a 

 point about half way on its length and widens into the roughened distal end. 

 The terminal surface has two chief articulating faces, one concave, the other 

 smaller and convex, for the reception of the carpals. The total length of the 

 radius is 290 mm. or practically the same as in M. robustus. 



The bones of the fore feet are not all preserved, but most of the metacarpals 

 and phalanges are represented. These seem to be nearly identical with those 

 of Owen's species, but are a trifle larger and slenderer. Digits 1, 2, and 3 were 

 provided with powerful claws; digits 4 and 5 were clawless, and terminated in 

 blunt, rounded ossicles. The first ungual phalanx (Plate 3, fig. 10) measures 

 90 mm. in extreme length and differs from the others in having a stem some 

 25 mm. in length, the long axis of which is bent at an angle with that of the claw- 

 bearing portion. This angle seems much greater than in M. robustus. The 

 proximal face is slightly concave. The bony core of the claw is some 55 mm. 

 long, laterally compressed, and regularly tapering in side view to a blunt point. 

 The basal half is surrounded by a thin bony sheath whicli l)ecomes much thick- 

 ened and rugose at the base ventrally (Plate 3, fig. 10). 



The second ungual phalanx (Plate 3, fig. 9) is without a stem-like proximal 

 portion, but the base articulates directly with the next phalanx by means of 

 two concave facets which are contiguous in the median line, and have their 

 greatest length in a dorso-ventral plane. The sheath at the base of the bony 

 core is extensive, some 45 mm. long laterally. The bony core of the claw is 

 90 mm. long, shghtly decurved, with a thickness from side to side of 26 mm. 

 near the middle. It tapers abruptly to a blunt and rather flattened point. 

 An angular ridge marks off the flattened ventral surface of the claw. The 

 phalanx next proximal to this is short, 53 mm. long, with two rounded facets 

 anteriorly, and a broadly concave facet posteriorh-. On each side of the latter, 

 at its ventral corners, is a small squarish facet which evident^ articulated with 

 a sesamoid. 



The third clawed phalanx (Plate 3, flg. 8) is extraordinarily large and power- 

 ful, 180 mm. in extreme length. It is shaped in general like that of digit 2, except 

 that it is more falcate and its inner side has a broad and .shallow sulcus beginning 

 near the summit about half way to the point and increasing in breadth and depth 

 to the tip, which it entirely encompasses. The ventral pad for the attachment 

 of tendons is broad, rounded and flattened, about 78 mm. in length from the 

 proximal border of the phalanx. Dorsally the bony sheath extended at least 

 63 mm. from the base of the claw, and thence forward and downward to the apex 



