22 POEBROTIIERIUM. 



Its extremity is broken in the specimen. The symphysis also is broken away, bnt 

 it appears to have commenced from behind about four lines in advance of the second 

 premolar, and the anterior mental foramen is situated just above this portion of it. 

 Dentiiion. — I think it probable that the permanent dentition of Poebrofherimn 

 was equal to the following formula : — 



. 0? 0? 1? 1? 4 4 3 3 go 



/. c. p.m. m. =00. 



4? 4? 0? 0? ^ 4 4 3 3 



la the specimen, the symphysis with its teeth is broken away; and a portion 

 only apparently of the upper canine alveolus remains. 



Supcrio)- Molars. — The upper teeth, in the specimen, consist of the three per- 

 manent true molars, fully protruded, and the three temporary molars, forming 

 together a closed row, and separated from this by a hiatus with an acute concave 

 margin about four lines long, is, what I susj^ect to be, the first permanent premolar, 

 which had no predecessor. (Figs. 1, 3.) 



The permanent true molars resemble those of the Musks, but their constituent 

 lobes possess much less prominent summits. The inner lobes also are less angular, 

 but more convex internally, and the outer lobes are much less prominent in the 

 same direction. The outer lobes of each true molar, in the Musks, are separated 

 by a narrow cleft, but in Poebroilierium they are separated only by a longitudinal 

 ridge, which is the most prominent of those existing externally. The median 

 ridge of each lobe externally is the most prominent and convex in the Musks, 

 but is relatively narrow in Poehrotherium , and the intervening spaces are more flat 

 in this genus. 



In the specimen under consideration, the last molar had been but a short time 

 fully protruded, the enamel being worn only from the summit of its postero-internal 

 lobe, and remaining nearly intact upon the postero-external. The summits of all 

 the other lobes of the true molars present narrow tracts of exposed dentine sur- 

 rounding the interlobular pits of enamel. 



The temporary molars, also, have a very great resemblance to those of the Musks. 

 The last of the series is like the permanent true molars, and in the specimen the 

 enamel has been worn from the masticating surface, except a small crescentic islet 

 between the posterior pair of lobes. 



The second temporaiy premolar in the specimen has its enamelled triturating 

 surface obliterated, and in its present condition is constituted by a wide posterior 

 lobe, the result of the confluence of an original transverse pair, and a narrower 

 anterior lobe with a pyramidal summit, which does not distinctly appear to be 

 formed from the association of an antero-posterior pair, such as exists in the corres- 

 ponding tooth of the Musks. Externally this tooth presents three convex promi- 

 nences, separated by concave depressions. 



The first temporary premolar has a simple, broad, oblong, trenchant crown, which 

 is most prominent at its anterior part. It is convex externally, and the enamel 

 internally is worn off" in a sloping manner. 



The first permanent premolar, which, as before observed, is removed from the 

 others by a hiatus, has a simple oblong, trenchant crown like that last described. 



