Nov\ 1847,] 323 



lias four ridges corresponding to those of the true molars. The third pre- 

 molar, or the one immediately preceding the last, has upon its crown a 

 posterior pair of thick crescents, and an anterior cusp which has the appear- 

 ance of being formed by the blending together of a pair of crescents. Ex - 

 ternally it is trilobed, the lobes being separated by two concave depressions. 

 It is shorter but broader than the last. The second premolar is com- 

 pressed, faintly trilobed, and presents an elongated trenchant crown. The 

 first premolar is the most remarkable characteristic of this cranium. It 

 is separated from the others by a concave notch of .333 of an inch, and is 

 on a line with the anterior mental foramen. It is implanted in the jaw by 

 two fangs, which are divergent and placed one anterior to the other. The 

 body is nearly as broad as the second premolar and is of a compressed pyra- 

 midal form, and the crown has a trenchant edge, the posterior and anterior 

 part of which form an angle about its centre. 



In the lower jaw, in the specimen, are six inferior molars iu a closed 

 row commencing .25 of an inch anterior to the corresponding six molars 

 above, and continuing as far back as the latter. Besides these, and separated 

 from them by a concave descending notch of .45 of an inch, just anterior 

 to the anterior mental foramen, or .15 of an inch anterior to the commence- 

 ment of the sympyhsis posteriorly, is one half of an alveolus for an addi- 

 tional or seventh molar, which, when the specimen was first received, con- 

 tained a portion of a fang, since mislaid. This additional molar in the 

 lower jaw is possessed by only one other known genus of Ruminantia ; the 

 Dor cat her ium, of Kaup. 



The crowns of the inferior molars are enveloped in the matrix in such a 

 manner that they cannot be exposed without endangering the specimen. 

 Externally the three true molars present their columns as sharply triangu- 

 lar prisms, as in Ovis, &c, and have no intervening points or cones, as in 

 Cervus, Dorcatherium, c. 



The fourth premolar is tri-lobed externally, each lobe presenting a cusp 

 towards the crown. The third and second are compressed, and the latter, 

 I can perceive, has a trenchant crown. 



The position of the molars, though resembling that of Dorcatherium, con- 

 siderably more than that of any other genus of Ruminantia, differs materially 

 from it, for while the teeth reach to the symphysis in the latter, in the for- 

 mer they even extend anteriorly to its commencement. 



From the foregoing description of the teeth, it will be perceived, that in 

 the possession of a seventh molar in the upper jaw, in the position of the 

 molars, and in several other minor peculiarities, this genus differs from all 

 others heretofore known, and is well characterized, and I therefore propose 

 for it the name of ," Poe'brotheridm."* 



The base of the maxilla inferius presents a double curve, and has its an- 

 terior, central, and posterior parts very nearly on the same line, so as to 

 give the lower part of the face an unusual degree of squareness. The angle 

 is prolonged upwards and backwards into a well marked and hook-like pro- 



* no* herba, (Ipom pasco, d-mpfera. 



