FREE INSTITUTE OF SCIENCE 



MASTODON 



appears to have consisted of two pairs of lobes and a single posterior lobe, 

 or talon. There are several irregularly placed tubercles on the outer side 

 between the first and second pairs of lobes, and the cingulum is raised into a 

 conical, crescentic eminence on the inner side, opposite the valley dividing the 

 lobes. The tooth is well worn, and exhibits irregular areas of dentine. This 

 tooth was implanted by two very long roots. 

 Its measurements are as follows : 



Width across posterior lobes ...... 27 mm. 



Height of crown on outer side . . . . . . 13 " 



Depth of remaining portion of root . . . . 37 " 



The third right lower milk molar, plate iv. fig. 5, consists of three pairs 

 of lobes and a posterior pair of cones. The cingulum, which everywhere 

 shows a tendency to rise into little cones, is well developed on the outer side, 

 and in front sends up a considerable prominence. The outer lobes are con- 

 nected by the usual fore and aft buttresses, while much smaller buttresses are 

 developed on the first and second outer lobes. The posterior lobes are very 

 little abraded ; the anterior end of the crown shows considerable wear from 

 the impact of the preceding tooth. 



Subjoined are measurements of this tooth : 



Length .......... 73 mm. 



Width across anterior pair of lobes . . . . . 32 " 



Width across posterior pair of lobes . . . . 45 " 



Height of inner anterior lobe . . . . . . 26 " 



Height of inner posterior lobe . . . . . . 32 " 



Plate iv. fig. 1 2 represents the crown, imperfect at the fore part, of what I 

 suspect to be an upper third milk molar of the left side. It nearly resembles 

 in constitution the complete specimen of the last upper premolar, but is con- 

 siderably smaller. All the lobes are worn at their summits in the usual 

 proportion, most in the anterior pair and least in the third inner one. 



The inner lobes are divided by furrows, each into a pair of sublobes, and 

 these exhibit in front and behind variable buttress-like ridges. The outer 

 lobes have the usual three offsets appearing as anterior, posterior, and medial 

 buttresses. The summits of the second and third outer lobes exhibit broad 

 elliptical dentinal areas with three small medial processes. The second inner 

 lobe exhibits a transverse figure-of-eight dentinal area, while the succeeding 

 inner lobe is only sufficiently worn to exhibit minute dentinal islets on its sub- 

 lobes. At the back of the crown a thick pyramidal process of the basal ridge 



