180 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



3| lines ; this is the anterior lobe ; the posterior one is narrower. 

 Each fang is longitudinally excavated at the surfaces next each 

 other ; and the outer part of the root, so defined, is thicker than the 

 inner part. 



The crown of the penultimate molar is in length 1 iach 9 lines, 

 ia breadth 1 inch 3 Imes, in height 8 lines : the dentine is exposed 

 at the summit of each ridge. 



The two ridges or bilophodont type of the molars of Nototherium 

 were indicated rather than demonstrated in the specimens Nos. 

 1505, 1506, and 1507*, on which the genus was founded. The first 

 complete lower molar which I have yet seen is the penultimate one 

 of the jaw under descriptionf. The crown is girt at the base by a 

 cingulum, developed behind into a low talon, and interrupted at the 

 outer and inner end of the main ridges, and for a greater extent at 

 the inner than at the outer sides. 



The horizontal contour of the crown is rather rhomboid than qua- 

 drate ; for the hind lobe is more internal in position than the front 

 one : and the ridges run, not in a line directly across the alveolar 

 border, but from without inwardly and a little backwardly. The 

 fore part of the outer end of each ridge is a little produced, most so 

 in the hinder one, in which the produced part, inclining inwards, 

 terminates, or abuts below, upon the middle of the base of the front 

 ridge : the anterior part of the inner end of each ridge is a little 

 produced forward, in an angular form ; the general result is, that 

 the summit of each ridge is slightly concave forward, convex back- 

 ward. 



The enamel is, for the most part, smooth and poHshed : the deli- 

 cate striae of growth are well marked, when viewed by a pocket 

 lens, on the outer side of the tooth, and the same power brings into 

 view a few punctations on the hinder slope of each ridge : the 

 enamel is rather thicker on this slope than on the front one, and 

 seems more so from being more obliquely abraded, from before 

 downward and backward: so exposed, the coronal surface of the 

 enamel is a line in thickness : the tract of dentine abraded in the 

 present tooth is 2 lines across. The hinder talon, or part of the 

 cingulum, is most developed : the front one seems as if destroyed by 

 pressure of that of the preceding molar. 



The antepenultimate tooth, or third counting backwards, measures 

 1 inch 6 Unes in long diameter, and 1 inch 2 Unes across the 

 hinder lobe : the talon at the back of this lobe is as well developed 

 relatively as in the penultimate molar : there is the same ridge or 

 production from the outer and front angle of the back lobe obliquely 

 towards the middle of the front lobe : much of this lobe has been 

 broken away. The two fangs of the second molar show a fore and 

 aft extent of at least 1 inch 2 lines for the crown of that tooth, 

 with an extreme breadth of 8 lines. That a still smaller tooth 

 preceded it is indicated, as before remarked, by a part of its socket. 



* Mus. CoU. Chir. 



t It shows the accuracy of the conjecturally dotted outline of the grinding 

 surface of the entire molars, given in plates 3 and 4 of the ' Eeport.' 



