PURBECK FORMATIONS. 57 



the base of the hinder inner cone (c). A less thick ridge extends from the fore part of 

 the outer lobe (a) from its base half way or more to its summit, and bounds the fore part 

 of the crown, being continued to the base of the front inner lobe (5) ; this anterior talon 

 or ridge [d ) is less developed in the anterior than in the posterior of the two molars of 

 the left side ; the hind ridge or talon is also less developed, and it is to the diminution of 

 the accessory parts {d and e) that the smaller size of the anterior of the two left molars is 

 chiefly due. The two best preserved molars of the right maxillary are more equal in 

 size and similar in character; they show the convex bulge of the inner surface of the 

 two main inner cones. The third molar, which may be the hindmost, is not sufficiently 

 entire for useful description, but the indication of the division of the inner wall of the 

 crown into the two main cones is unmistakable. 



The same characteristic sculptuiing of the enamel which was noted in the preceding 

 specimen is conspicuous in the best preserved teeth of the present, viz. the vertically 

 ridged summits of the chief cones, the ridges being comparatively thick, few, and con- 

 verging toward the apex. The sides of the main cones turned toward each other are 

 shorter and less vertical than those forming the outer and inner surfaces of the crown. 

 The inner side of the outer cone extends a short way between the outer sides of the two 

 inner cones. 



Again and again have I gone over all the mandibular specimens and fragments of 

 lower jaws in quest of teeth approximating sufficiently in character with the well-marked 

 upper molars above described, but in vain. Had there occurred any Purbeck mandibular 

 specimen allied to the Oolitic Stereognatlms, it might have suggested a relationship to the 

 maxillary evidences of Bolodon crassidens. 



liicertce sedis. Plate III, figs. 14, 14 a, 14 b, 16 a, 16 b, .20. 



The subject of fig. 14, PI. Ill, is a portion of a right mandibular ramus, with parts of 

 two molars {a) ; with the intervening sockets of, seemingly, the last premolar and the first 

 and second molars, and with a mutilated premolar in advance of that (Jj) in place. 



The chief value of this specimen is its demonstration of a broad triturating surface, 

 such as might be produced by attrition against upper molars of the breadth of those in 

 the preceding specimen. But the antero-posterior length of the best preserved molar (a) 

 in the present mandible forbids a reference to Bolodon. The last molar, or what seems to 

 be such (c), is about one third the size of the antecedent tooth (a), with a low one-lobed 

 crown, the enamel of which is feebly wrinkled on its outside near the grinding surface. 

 It may answer to the small tubercular in Thylacoleo and Plagiaulax. The premolar [h) 

 has a low but sharp-pointed chief cone, thick, convex externally in proportion to its 

 height; the hind cusp is well developed. The state of this specimen forbids me to 



