48 • [April, 



bertson, the same gentleman who lately enriched our collection by the deposit 

 of the cranium of Poebrotherium, described in the number of the Proceedings 

 for Nov. and Dec, 1847. 



One of the fragments is a small portion of the upper jaw of the right side, con- 

 taining the posterior two molar teeth, and attached to a jrartion of the same kind 

 of matrix, which partially enveloped the cranium of Pocbrotherium. The two 

 teeth are perfect, with the exception that the antero-external demicone of the 

 penultimate molar is broken away. The penultimate molar has four fangs, the 

 interna! ones of which are divergent from the external. The last molar was just 

 upon the point of protruding so that the crown only is formed. 



The other fragment is a portion two inches long of the right side of the infe- 

 rior maxilla, and contains the posterior three molars. The internal half of the 

 crown of the antepenultimate molar is destroyed, as is also a small projecting 

 point on the internal surface of the penultimate molar. The last molar is in the 

 same condition as the corresponding superior tooth. The external part of the 

 upper enameled surface of the crown of the antepenultimate molar is worn away 

 from the outside inwardly, as is also the edge of the same part of the crown of 

 the penultimate molar. 



The enamel is thin and about as rugose as that of Cervus virginianus. 



The molars, like those of Merycopotamus,' have the antero-posterior cleft di. 

 viding the primary lobes, forming two bends triangular convex,' inwards in the 

 superior teeth, outwards in the inferior teeth; producing a crown having the 

 ruminant pattern. 



The inner demicones of the superior molars are triangular convex. Their 

 inner surface inclines outwards from the base, at an angle of 65 degrees, and is 

 a very little concave in this direction. 'I"he outer surface is concave, inclined at 

 an angle of about 50 degrees, and runs into the outer demicones at the depth of 

 from three to three and a half lines from the apex of the latter. "The exposed 

 part of their base is surrounded by a projecting ridge, about one-fifth of a line 

 deep on the anterior and posterior sides of the tooth, and perceptible internally 

 merely as a slight rising of the base, excepting opposite the interlobular depres- 

 sion, where a small irregular and rather inconspicuous tubercle exists, apparently 

 formed by the union of the ridge of the two internal demicones at this point, but 

 no ridge passes from this tubercle outwards into the interlobular fissure as in 

 Merycopotamus. 



The inner demicones fold around the external convexities of the exterior demi- 

 cones. The antero-external edge of the enamel fold of the postero-internal demi- 

 cone projects a line or more between the postero-external edge of the antero in- 

 ternal demicone, and the postero-external demicone, causing the latter edge to 

 bend abruptly forwards towards the antero-external demicone. 



The points of the exterior demicones project above those of the interior, less 

 in the last than in the penultimate molar. The internal surface is triangular con- 

 vex, with a little vertical inclination. The external surface is concave from side 

 to side, nearly vertical, and is slightly elevated in a vertical line in the middle. 



The postero-external angle of the postero-external demicone of the penultimate 

 molar, forms a strong, rounded, vertical prominence, which in the last molar is 



* Vol. 2, pi. 140, Fig. 8, 



