320 I'AL^OTHERIUM. 



The last molar tooth has a more oblong crown than the 

 preceding ones, the grinding surface of the tooth being 

 more extended in the axis of the jaw ; but the posterior 

 margin of the tooth is narrower, and the crown approaches 

 more to the triangular form. In the collection of S. P. 

 Pratt Esq., F.G.S., there is a fine specimen of the germ 

 or newly-formed crown of the last molar tooth, from the 

 right side of the upper jaw, fig. 112. 



The two concave enamelled surfaces, d, d, separated 

 by the three salient ridges, which form the outer wall 

 of the crown, are strongly inclined inwards as they extend 

 downwards; and each concave surface is produced into 

 a point : the enamelled summits of which are entire. 

 Descending folds of the formative matrix of the tooth 

 have left corresponding sinuous depressions on the surface 

 of the crown : one of these (5) extends in a sigmoid form 

 from the internal to near the middle of the external 

 wall ; a second, (a) which begins by a deep fossa at the pos- 

 terior border of the tooth crosses the preceding, and extends 

 to within a short distance of the anterior border : a ridge is 

 continued from each external angle of the crown first down- 

 wards, and then inwards to the opposite internal angle ; at 

 the posterior angle it is continued into a prominent conical 

 lobe ; the ridge continued to the anterior angle surrounds 

 the base of a larger and higher one, which Cuvier has 

 termed the intermediate lobe. At the commencement of 

 mastication, the dentine is first exposed upon the outer zig- 

 zag ridge, and being bound by two parallel lines of ena- 

 mel, a double crescent is produced, like that on the outer 

 half of the tooth of a Ruminant quadruped ; but as masti- 

 cation proceeds in the Palseothere, the second or internal 

 crescent of enamel is soon obliterated. The field of den- 

 tine is widened and bounded by the peripheral ridge of 



