284 



The crown of the first (d 3) is worn down to a flattened uniform surface, showing the same 

 posterior breadth as in the entire crown in the immature jaw. The two roots supporting 

 it have now risen nearly half an inch above the socket. The dimensions and proportions 

 of the following four grinders closely accord with those in the mandible, the teeth of which 

 are figured of the natural size in Plate XLIII. fig. 3. 



In the part of the right ramus of Nototherium Mitchelli with the three last molars 

 and the back part of the symphysis, the molars are worn nearly to the same degree : 

 their antero-posterior extent is 5 inches 2 lines. The left ramus of the same species, 

 more mutilated anteriorly, but with a greater proportion of the ascending branch, 

 shows the last two molars similarly worn. The enamel in these Nototherian specimens 

 is as thick as in Dtprotodon. 



In a mandibular fragment with the lobes of the last molar worn down to the valley, 

 the anterior root of the penultimate molar is exposed, showing a strong curve convex 

 forward, with a deep anterior longitudinal indent almost dividing the implanted end 

 (Plate XLIV. fig. 8). The fine rugosity of the cement, repeated on the closely clasping 

 wall of the socket, is here well shown. 



The molars (Plate XLIV. figs. 4, 5, 6) in the mandible of Nototherium Victoria; (Plate 

 XLI.) show nearly the same stage of attrition as in the Worcester specimen of N. Mitchelli 

 (Plate XLIV. fig. 3). 



As already stated, they are limited to the last three teeth and a fragment of the one 

 in advance. In m i the ridge closing the outer entry of the valley (/«, figs. 4 & 5) 

 developes an enamel tubercle ; and there is a smaller one at the inner entry (h 1 , fig. 6). 

 Of this there is no trace in the perfect specimen of that molar in the immature jaw of 

 Nototherium Mitchelli (Plate XL.), and only a very feeble indication of such on the outer 

 side. The rudiment of the " link " or ridge (r) from the hind lobe to the middle of 

 the base of the hind surface of the front lobe is well marked in N. Victorice. The hind 

 talon (<j) closely overlaps so as to interlock with the front talon (f) of the penultimate 

 molar, m 2. The abraded surfaces of the two lobes slope from before downward and 

 backward. The fore-and-aft diameter of m 1 is 1 inch 6 lines. 



The fore part of the penultimate molar (fig. 4, a, m 2) rises half an inch above the 

 overlapping talon (g) of the antecedent tooth, at the outer and inner ends of which the 

 front talon of m 2 appears. Externally- it curves up to terminate near the base of the fore 

 and outer part of the front lobe ; on the inner side it sooner subsides. The greater 

 breadth, as compared with m 1 of the front lobe, is gained chiefly by extension of the 

 inner part. A ridge, beginning at the back part of the outer end of the front lobe, 

 curves down to the outer entry of the valley, developes there a tubercle, and curves up 

 the outer side of the hind lobe, whence a similar ridge curves downward and backward 

 to the hind talon ; the middle and thickest part of this is undermined by the smooth 

 surface which overlies the front talon of the last molar (f, m 3). 



The fore-and-aft extent of m 2 is 1 inch 9 lines ; the transverse breadth of the front 

 lobe is 1 inch 2\ lines, that of the hind lobe is 1 inch 1 line. The abraded surfaces 



