A NEW MYLODON. 337 



of the ventral disc for tendinous insertion. Apparently the bone is more com- 

 pressed and deeper than in M. robusius. 



It was upon a third ungual phalanx and some other phalanges from Oregon 

 that Cope (1878) based his Mylodon sodalis. He says that the bony sheath 

 at the base of this large claw is developed on but one side only, and that its place 

 on the opposite side is taken by a prominent rim, tuberculate and notched. His 

 figure, subsequently published (Cope, 1889), seems to indicate a sheath covering 

 the basal third of the claw. The measurements are not very different from 

 those of the specimen studied, but indicate perhaps a slightly more slender claw- 

 bearing portion. Comparative measurements are given under the heading of 

 Mylodon sodalis. 



The terminal phalanx of the fourth digit (Plate 3, fig. 11) is bluntly pointed 

 witli a deep notch about half way on its ventral outline. It is 44 mm. long and 

 articulates with the cotylus of the next proximal phalanx by a facet of an inverted- 

 heart shape, whose lateral portions are very slightly concave. 



The fifth digit ends in a small rounded button of 23 mm. in greatest breadth. 

 The next proximal phalanx is an irregularly rectangular bone in dorsal aspect, 

 42 mm. long, and not so compressed as that of M. 7-obustus. 



Of the pelvis a portion only can be reconstructed from the fragments. This 

 constitutes about a third of the right-hand shield external to the acetabulum, 

 the distance from which to the outer corner is about 250 mm. Along the superior 

 margin there is a rim turning forward at nearly right angles, and of gradually 

 increasing width, as in M. robustus. Its edge is roughened and slightly tubercu- 

 late for muscle attachment. The structure of the pelvic plate is rather char- 

 acteristic; the superficial portions are of densely formed bone, while between is 

 a central layer of a porous or cancellar nature. The three layers are rather 

 sharply marked off. 



The fernur is of the same type as that of M. robustus, but differs in a few 

 minor details. That of the right side is the better preserved and has an approxi- 

 mate length of some 500 mm., a trifle greater than in Owen's specimen. It 

 shows the concave outhne of the inner side, when viewed from in front. The 

 great trochanter extends as a roughened ridge about half the outer length of 

 the shaft. The condyle is large and somewhat hemispherical and differs from 

 that of M. robustus as figured by Owen in that the depression for the ligamentum 

 teres is of triangular outline, with the point toward the center of the condyle 

 whereas in Owen's specimen it is broad and expands into a rounded depression. 

 The part of the femur between the condyle and the great trochanter seems 



