Cope.) ts [April 7, 
those hitherto known, three of them of a size equal to that of the I. 
jeffersonit, the others smaller. These species are only certainly distin- 
guishable at present by the teeth, as the other bones are very similar to 
those of other species, so far as preserved. 
The teeth consist of eighteen canine, and nineteen molar teeth, whose 
characters are discussed below. The bones are chiefly those of the feet, 
with portions of long bones, and numerous vertebra. Cranial bones are 
in most instances destroyed, for though several complete crania were ex- 
humed, the exposure to frosts and thaws with snow and rain, as they 
laid in the piles of material, disintegrated them. Of limb bones there are 
the extremity of a large tibia with cotylus for astragalus, several extrem- 
ities of fibula, and some broken heads of femora. 
Of the bones of the fore limb there are three unciforms, two magnums, 
and fifteen metacarpals with numerous phalanges. The bones of the 
hind limb include three astragali, seven cubiods, six scaphoids, and five 
incomplete metatarsals. The phalanges of both fore and hind feet, which 
much resemble each other, number thirty-two, of which nine are ungueal, 
Of vertebree, no cervicals have been found, except an axis without neural 
arch. Caudals are most numerous ; some of the vertebra have codssified 
epiphyses, others not, indicating various ages. I have counted twelve 
individuals from the teeth, but it is quite possible that there are others 
represented by some of the bones. 
The canine (molar) teeth present a remarkable variety of forms. As is 
known, the section of the crown is oval, on one side concave with a more 
or less prominent swelling interrupting it. The differences are seen in 
the development and position of the broad rib of which the swelling is a 
section, in the curvature of the shaft, and greater or less obliquity of the 
grinding surface. 
There are three types of form among them as follows : 
ist. The shaft curved, the triturating surface oblique, the internal 
longitudinal rib prominent, nearer one end of the crown than the other, 
dentine of inner side thickened anteriorly ; two specimens. 
2d. Shaft nearly straight, triturating surface transverse (in its long 
direction); rib of inner face median, prominent ; dentine of inner side 
uniformly thin. 
8d. As in the last, but the shaft more compressed, therefore the 
section narrower, the inner bulging rib being very low and insignificant. 
The first of these represents a species distinct from those of the other 
series; one nearer the W. jeffersonii, and of large size. 
In studying the present genus I have been under many obligations to 
Dr. Leidy’s Memoir on the Extinct Sloth tribe of North America, pub- 
lished by the Smithonian Institute in 1855. In it the species Megalonyx 
jefersonit is established for the first time on a solid foundation, and the 
characters, especially of the dentition, clearly pointed out. 
M2EGALONYX LOXODON, Cope, species nova. 
The two teeth of the first type may, perhaps, be superior ones; their 
curvature accounts for the obliquity of the grinding face in the long 
