512 



The degree of abrasion of the three anterior molars in place (d a, d 4, m 1), when the 

 penultimate molar (7712) has partially emerged and the last molar (m?) has pushed the 

 summit of its crown through the bony cell (the walls of which were in part broken 

 away in the fossil), confirms the ascription of the molars (Plate XXIV. figs. 1, 2, 5, 6, 

 9, 12, copied from the original Plate of 1845) to one and the same young individual 

 Diprotodon. 



When folio 13 of the present work was struck off I had not received any specimen 

 of d s (p. 203), and based my description of the tooth on the indications of its socket 

 and the sketch of the tooth in situ sent to me in 1848. The confirmation of those 

 grounds of restoration, afforded by the subject of Plate CXXIV. 3, was most accept- 

 able, inasmuch as it placed beyond question the generic distinction between Diprotodon 

 and Nototherium afforded by the foremost molar tooth (d s). The two transverse ridges 

 (fig. 3, da, a, b) have been abraded by attrition against corresponding transverse ridges 

 of the opposing molar (d s) of the upper jaw. The homologous molar (d 3, Plate XLIII. 

 and figs. 11 & 12, Plate LXXXVIII.) of Nototherium required the same degree of 

 modification of the mandibular milk-molar (d s) figured in Plate XL. Under present 

 evidence fragments of either upper or lower jaw with the entire anterior molar (d 3) 

 of a Diprotodon or a Nototherium would at once reveal their generic character to the 

 palaeontologist conversant with the dentition of these huge extinct Marsupials. 



The descriptions of the lower molars of Diprotodon in pp. 204-208 precludes the 

 necessity of further dwelling on the acceptable subject of the subjoined Plate. 



PLATE CXXIV. 



Diprotodon australis. 



Fig. 1. Outside view of part of mandible and mandibular teeth of a young individual. 

 Fig. 2. Inside view of the same. 



Fig. 3. Grinding-surfaces of the first three molars and of the coronal portions of the 

 undeveloped last two molars of the same. 



Genus Nototherium. 



§ 1. Specific Characters of deciduous Molars, ds, d 4. — Since the printing off of 

 folio 23 and Plate XLIII., descriptive and illustrative of the dentition of the upper 

 jaw of Nototherium Mitchelli, I have been favoured with the opportunity of studying 

 certain teeth (d 3, d 4, e. g.) which previously I knew only through photographs or 

 plaster casts. Thus I have now the certitude that the trilobed character of the 

 outer half of the upper milk-tooth (d 3) is natural ; but the cast from which were 

 taken figs. 3 & 4 of Plate XLIII. shows it rudely, and minor characters of the tooth 

 are obscured through imperfect moulding. I therefore give figures, taken from the 

 tooth itself, in Plate LXXXVIII. figs. 11-14, d». The trilobed outer surface is an 



