514 



Nototherium inerme, as exemplified in Plate XLIII. fig. 5, rfs, has a still more sim- 

 plified and relatively smaller anterior milk-molar. 



Only the hinder of the two outer channels in Nototherium Victoria is here present, 

 anterior to which the convex enamel-wall is continued to the fore angle of the crown. 



The differences between the ds, d a of Diprotodon (ante, p. 204) and of Nototherium 

 are well marked and constant. 



§ 2. Mandible of young individual. — The dental characters of the species (N. inerme) 

 have been yielded chiefly by those of the maxilla*. The teeth of the type specimens 

 of mandible were too mutilated to yield them satisfactorily f. Since its description I 

 have had the pleasure to receive a right mandibular ramus of a young individual with 

 t he teeth at the same phase of development as in that of Nototherium Mitchelli 

 (Plate XL.), and similar views of the mandible of Nototherium inerme are therefore 

 given in Plate CXXV. The specimen was discovered by George F. Bennett, Esq., 

 at Gowrie, Darling Downs, Queensland, and was transmitted to me by his father, 

 Dr. George Bennett, F.L.S., in 1874. 



The crown of d 3 is mutilated, but sufficient remains to show that it accords with the 

 generic type of Nototherium (Plate XL. d s), and is not bilophodont as in Diprotodon ; 

 sufficient also to give its antero-posterior extent, which agrees with that in its homotype 

 of the upper jaw (Plate XLIII. fig. 5, dz). The next tooth (d*), first of the bilopho- 

 dont series, shows the same fore-and-aft extent as d i above, but, as usual, is narrower 

 transversely (Plate CXXV. fig. 3). The ridge of enamel which in Nototherium Mitchelli 

 descends obliquely inward from the fore part of the outer angle of the hind ridge or 

 lobe to terminate near the middle of the valley is not present in d 4 of Nototherium 

 inerme. In m i the ridges which define the concavity of the front surface of the fore 

 lobe in Nototherium Mitchelli are not so developed in Nototherium inerme ; but at the 

 back of the fore lobe there is a mid vertical prominence not shown in N. Mitchelli; 

 the front surface of the hind lobe of d \ in Not. inerme lacks the ridge of enamel from 

 the outer angle which gives, or adds to, the transverse concavity of that surface in 

 Not. Mitchelli. 



The molar (m i), like the two preceding teeth, shows the same agreement in fore-and- 

 aft extent with its homotype in the upper jaw (Plate XLIII. fig. 5), viz. 1 inch 3 lines. 

 The summits of the two lobes of m i show wear in a greater degree than those in the 

 young jaw of Not. Mitchelli (fig. 3, Plate XL.). The unworn summits of m 2 in Not. 

 inerme (Plate CXX. figs. 3 & 4) have risen to the top of its alveolus and have begun 

 to protrude therefrom. But the increased size of the jaw and the proportion of the 

 depth to the length of the ramus are greater than the slight advance of age would 

 account for, and must be put to the specific distinction of Nototherium inerme. 

 Whether there may be arrest of the vertical growth in the course of acquisition of the 

 mature length of the mandible is questionable ; but if the proportions of this young 



* Ante, pp. 275, 277 ("minor relative size of d 3"), Plate XLTII. fig. 5. 

 + Ante, p. 271, Plate XLII. 



