228 REPORT — 1844. 



tent of the base of the crown of this tooth is one inch nine lines ; the breadth 

 of the crown is one inch three lines ; the height of the crown one inch two 

 lines ; the length of the posterior fang was two inches when entire. 



The fifth specimen is the crown of the penultimate molar, left side, lower 

 jaw, of apparently the same individual Diprotodon australis. The anterior 

 transverse ridge had just begun to be worn : the summit of the posterior 

 ridge is entire. This is not divided into small mammilloid tubercles as in the 

 Dinotherium, but is irregularly and minutely wrinkled as in the Tapir. In 

 the depth of the cleft between the two transverse ridges, the teeth of the Di- 

 protodon resemble those of the Tapir more than those of the Kangaroo ; 

 Ijut the eminences are higher and more compressed than in either of those 

 existing genera. In the largest existing species of Kangaroo, as the Macro- 

 pus major and Macropus laniger, the lower molars have no posterior talon 

 or basal ridge, but this is present in the still larger extinct species of Kan- 

 garoo, called Macropus Atlas, in which, however, it is much smaller than the 

 anterior talon. In the Tapir the anterior talon is also larger than the posterior 

 one, but in the Diprotodon the proportions of the two basal ridges are reversed. 

 The reticulo-punctate markings are i)resent at the anterior surfaces of the 

 enamel of the transverse ridges of the molars in the Tapir, whilst in the 

 Kangaroo and Dinothere the enamel is smooth and polished : the molars of 

 the Diprotodon are characteristically distinguished by the rugose punctate 

 markings in both the anterior and posterior surfaces of the transverse ridges. 

 The breadth of the crown of the present tooth is one inch and a half, and the 

 height of the entire posterior division is the same. 



The sixth dental fossil is the anterior part of the anterior transverse emi- 

 nence of the last molar tooth, left side, lower jaw, of the same Diprotodon 

 australis; it measures one inch nine lines across the base, and diminishes in 

 breadth more gradually towards the sununit than in the preceding tooth. 

 The summit of this eminence had just begun to be worn by mastication ; the 

 pulp cavity is continued into the basal third of the crown. 



These specimens which show the termination of the molar series, with the 

 anterior part of the jaw from the Condamine river containing the commence- 

 ment of the molar series, demonstrate the entire number of teeth in the lower 

 jaw which characterizes the genvts Dip^'otodon, viz. one incisor and five molars 

 on each side. In this formula the great Pachydermoid marsupial resembled 

 the Wombat, the Koala, the Potoroo, and the Kangaroo, although it is rare to 

 see the total number of true molar teeth at one time in the larger species of 

 Macropus. The lower incisors of the Koala in the subcompressed subqua- 

 drate form of their implanted base most resemble in form those of the Dipro- 

 todon, but the exserted crowns, like those of the Kangaroos, have an entire 

 covering of enamel which does not extend upon the inserted fang. In the 

 partial covering of the whole extent of the inserted base of the tusk of the 

 Diprotodon, we perceive a greater resemblance to the scalpriform incisor of 

 the Wombat ; and every analogy teaches that the exposed part of the tusk of 

 the Diprotodon must have had the same extent of enamel-coating as the in- 

 serted base. The Diprotodon, however, departs widely from the genus PJias- 

 colomys in the divided base and in the shape of the crown of its molar teeth : 

 in these more essential parts of the dental system it approximates Macropus 

 more closely than any other known Marsupial genus ; yet the double trans- 

 verse-ridged type of molar teeth is manifested by so many genera of recent 

 and extinct Manuifialia* of very different forms and organization that little 

 could be inferred as to the coexistence of the proportions of the Kangaroo 



* Tapirus, Lophiodon, Dinotherium, Mcinaius. 



