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vertically. The cingulum rises to a point, forming an angle upon the outer side of the 

 base of the anterior lobe (fig. 1, m i). The closing ridge of the valley is formed by its 

 continuation backward from the angle, and is limited to the outer entry. The hind basal 

 ridge (g) is thicker than in d 4. 



The two lobes are not on the same parallel, but rather " en echelon" the hind one 

 rising more mesially or internally, and its inner and fore angle looking forward clear of 

 that of the other lobe. The unworn summits are more bent backward than in d 4. 

 The fore-and-aft extent of m 1 is 1 inch 6 lines ; the transverse diameter of the base of 

 each lobe is 1 inch. 



In the partially exposed calcified germ of m 2 (ib. figs. 3 & 4) the summits of the two 

 lobes are not quite parallel, and the hind border of the hind lobe slopes more backward 

 to a well-developed basal ridge. 



The smooth shallow cavity behind the alveolus of m 2 is plainly the beginning of the 

 formative chamber of m 3, calcification of which had probably not begun. 



I regret not to possess specimens of Nototherium showing stages of mandibular 

 dentition between that above described and the subject of Plate XLIV. fig. 3. 



This specimen forms part of a collection of fossils from the deposits of Darling Downs 

 made by Henry Hughes, Esq., and now in the Museum of the Natural-History Society 

 of Worcester, to the Council of which I am indebted for the opportunity of examining, 

 comparing at the British Museum, and figuring instructive evidences of extinct Austra- 

 lian Mammals. The one which is referable to Nototherium is the right ramus of the 

 mandible with the last three molars in situ, the fangs of the second and part of the 

 alveolus of the first molar. The two fangs of the second molar (ib. d 4) show a fore-and- 

 aft extent of at least 1 inch 2 lines for the crown of that tooth, with an extreme breadth 

 of eight lines. That a still smaller tooth preceded it is indicated, as before remarked, 

 by a part of its socket (d 3). The shape of that tooth, generically distinguishing Noto- 

 therium from Diprotodon, is instructively shown in the preceding specimen (Plate XL.). 

 The antepenultimate tooth, or third counting backward (Plate XLIV. fig. 3, m 1), measures 

 1 inch 6 lines in long diameter, and 1 inch 2 lines across the hinder lobe ; the talon (g) 

 at the back of this lobe is as well developed relatively as in the penultimate molar. The 

 ridge (r) or production of the outer and front angle of the back lobe obliquely toward 

 the middle of the front lobe is conspicuous at this stage of attrition ; much of the front 

 lobe has been broken away. 



The crown of the penultimate molar (m 2) is in length 1 inch 8 lines, in breadth 

 1 inch 3 lines, 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 on which the genus was founded. The restoration 

 ventured on in the figures of these fossils* was verified by the molars in the immature 

 jaw subsequently sent by Leichhardt. The first complete penultimate molar which I 

 had the opportunity of studying showed the base of the crown girt by a " cingulum," 

 * " On the Extinct Mammals of Australia," Reports of Brit. Assoc. for 1844, p. 231, plate 3. fig. 1. 



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