THE OSTEOLOGY OF ELOTHERIUM. 275 
crown is long, massive, recurved, and bluntly pointed; it is oval in section, and has a 
prominent posterior ridge. 
The premolars are very simple in construction. The first three are well spaced 
apart and have compressed, but thick, conical crowns, without accessory cusps of any 
kind, and each is implanted by two fangs. In size, they increase posteriorly and p ® has 
a decidedly higher crown than any other premolar. P 4 is smaller than p 2 in every 
dimension except the transyerse, this diameter being increased by the addition of a large 
internal cusp (the deuterocone) and the crown is carried upon three fangs. In the 
smaller species of the genus, such as H. mortoni, p 2 and p 4 are placed close together, 
while in the larger forms these teeth are separated by a short space, and the diastemata 
between the other premolars and between p + and the canine are relatively somewhat 
greater, the enlargement of these teeth hardly keeping pace with the elongation of the 
muzzle. In the European species, #. magnum, the arrangement of the premolars is 
somewhat different, p 2, ® and 4 forming a continuous series, while p + and 2 are quite 
widely separated. 
The molars are relatively quite small; m 2 is the largest and m ? the smallest of the 
series. The crowns are low and bunodont, bearing six tubercles arranged in two trans- 
verse rows. ‘The hypocone, though functionally important, is decidedly smaller than the 
protocone, and structurally is still a part of the cingulum. Schlosser is, however, mis- 
taken in supposing that there is any important difference between the American and the 
European species of Hlotherium with regard to the position of the protocone. In m 3, 
which has a more oval crown than the other molars, the sexitubercular pattern is 
obscured by the development of numerous small tubercles upon the hinder half of the 
tooth. The cingulum of the molars is quite strongly marked, especially upon the ante- 
rior and posterior faces. 
B. Lower Jaw.—The incisors resemble those of the upper jaw, except that they are 
of more nearly equal size and somewhat more spatulate shape ; 1 y is little enlarged and 
is much smaller than the corresponding tooth in the upper jaw. 
The canine is a very large, recurved tusk, like the upper one in size and shape; it 
bites between the upper canine and enlarged external incisor, the three teeth together 
making up a very formidable lacerating apparatus. An interesting hint as to the habits 
of this animal is given by a peculiar mode of wear of the lower canine which occurs in 
some well-preserved specimens. In these we find a deep groove on the posterior face of 
the tooth, beneath the enamel cap and close to the level of the gum. No other tooth can 
reach this point to cause such a mode of attrition, and the groove is doubtless due to the 
habit of digging up roots with the lower tusks; the pull of the roots, especially when 
covered with sand or other gritty material, would naturally wear such a groove.* The 
* This ingenious and highly probable explanation of a somewhat puzzling fact was suggested to me by my 
colleague, Prof. C. F. Brackett. 
