222 NOTES ON A LOWER JAW OF PALORCHESTES AZAEL, 



the structure of the premolar. This tooth has a form peculiarly 

 its own, differing equally from the subtrenchant bitubercular tooth 

 of the former, and the long fluted, chisel-like tooth of the latter. 

 It is eight lines long and three lines broad, of a semioval form, 

 with its outer surface convex and sloping rapidly downwards. On 

 this aspect it has two shallow indents at about equal thirds of its 

 length, the posterior being the deeper and broader of the two. On 

 its inner surface it rises vertically from the socket into a median 

 lobe, separated from the fore and hind angles by indents, of which 

 the anterior is long and shallow, the posterior shorter and deeper, 

 each of them being separated from its anticlinal indent, by a short 

 median ridge. The apex of the mid lobe is worn down sufficiently 

 to expose an inwardly directed loop of dentine, and the general 

 shape of the tooth being reniform with the pelvis turned inward a 

 little more attrition would extend the dentine loop into the form of 

 an open double curve. The prebasal ridge of d 4 is developed on its 

 outer two-thirds only, and is connected with the anterior lobe by a 

 minute link. The anterior lobe, like all the other lobes of the teeth 

 in place, has on its anterior aspect a broad and shallow indent. The 

 median link is well developed and, rising from the middle of the 

 posterior surface of the fore lobe, subsides on the outer angle of the 

 anterior side of the hinder lobe. The post-basal ridge is equally 

 broad on either side of the mid link — in other respects it is as 

 described in the worn tooth by Prof. Owen. The same must be 

 said of the other characters of this tooth — nor can anything be 

 added of importance to Prof. Owen's description of m 1 itself. All 

 the teeth in place p 3 d 4 and m 1 are equally worn, in each there is a 

 narrow line of dentine exposed by the abrasion of the enamel. The 

 enamel of m 2 is of course intact, the hinder lobe of the tooth 

 having but lately risen fairly above the gum. The incisor is 

 remarkable for the unusual expansion of its base, at the incisive 

 outlet it measures twelve and a-half lines, a width exceeding its 

 whole length by more than one-fifth. Its inner edge, in opposition 

 to that of its fellow is straight, its outer has a parabolic curve from 

 the outer angle of the socket to the lip of the inner edge. The 

 internal or posterior surface is at the inner edge strongly concave, 



