285 



of the summits of these lobes slope, as in m 1, in the same direction but in a greater 

 degree. The hind root of m 2 is exposed by the fracture shown in figs. 1 & 2, Plate 

 XLI. ; it inclines somewhat backward as it sinks in the socket ; its basal breadth at the 

 outlet of the socket is 1 inch ; it contracts, in the same direction, to 7 lines ; much of 

 its surface shows minute granulate longitudinal striations. 



The last molar (Plate XLIV. figs. 4, 5, 6, m 3) rises above and projects inwardly beyond 

 the preceding, in the same degree as m 2 does in relation to m 1. The festoon character 

 of the ridges curving toward the outer entry of the valley and to the hind talon is repeated 

 in greater strength ; the outer closing tubercle (fig. 4, h) is less marked than in m 1, but 

 is conspicuous, as is that in the ridge closing the inner entry (fig. 5, h'). I incline to 

 regard these tubercles as constant, and as differentiating the last two molars of the present 

 species from those of Nototherium Mitchelli. A mere linear tract of dentine is exposed 

 on the obliquely worn apices of the transverse ridges of m 3. The fore-and-aft diameter 

 of this molar is 1 inch 10 lines ; the transverse extent of the abraded summit of the 

 hind lobe is 10 lines, but that of its base is 13| lines, the same diameter of the front 

 lobe being 15 lines. The enamel in Nototherium Victorias is not so thick as in N. Mit- 

 chelli ; its surface is similar. 



When the skull, or upper jaw, of this species may be found in South Australia, it will 

 yield, as in the case of the Queensland specimen, the characters ascribed by Macleay to 

 Zygomaturus, with, probably, better marked specific characters than those of the lower 

 jaw. 



§ 5. Conclusion. — No mandible or mandibular teeth, referable or adaptable to those 

 of the maxilla in the unique subject of Plates XXXVI. & XXXVII., have yet been dis- 

 covered, save those which yield the characters of the genus Nototherium. No skull 

 adaptable to the mandible and mandibular teeth of Nototherium has yet been discovered, 

 save that to which the name Zygomaturus was given. The admission, therefore, into 

 palseontological catalogues of two genera of bilophodont Marsupialia of the bulk of 

 Nototherium awaits the discovery of fossils demonstrating the distinctive characters of 

 such. 



Taking a retrospect of the dental characters of the genus Nototherium with reference 

 to a comparison with those of the genus Diprotodon, we find that the indications, few 

 and feeble though' they seemed in the mutilated mandibles and mandibular dentition 

 first received*, have been supported and the inferences therefrom verified in a striking 

 and unexpected degree by the characters of the rest of the skull and of the maxillary 

 dentition. 



The first molar, for example, does not give, in miniature, the bilophodont character 

 of the other and larger molars ; its crown answers rather to the outer half of the two- 

 ridged grinder with a rudiment of the inner half of the hinder transverse ridge or lobe. 

 This tooth, in fact, exemplifies the final stage of modification converting the longitudi- 



* Op. cit. 



