THE OSTEOLOGY OF ELOTHEKITJM. 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 - 3 has 

 a decidedly higher crown than any other premolar. P ^ is smaller than p - J - in every 

 dimension except the transverse, 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 E. mortoni, p £ and p ± 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 1 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, E. magnum, the arrangement of the premolars is 

 somewhat different, p 2 , 3 and ± forming a continuous series, while p 1 and *- are quite 

 widely separated. 



The molars are relatively quite small ; m ^ is the largest and m - s - 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 Elotherium with regard to the position of the protocone. In m ^, 

 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 ; i g- 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 sj)ecimens. 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. 



