Tertiary.'] PALEONTOLOGY OF VICTORIA. [^Mammalia. 



above measurements, this tooth in D. longiceps is distinguished from the corre- 

 sponding-ly worn homologous one of D. Atistralis by the abruptly small rounded 

 backward extension or lobe on the enamel on the hinder surface of the anterior lobe 

 of the tooth, corresponding with the strong rounded longitudinal ridge projecting 

 from the posterior face of the anterior lobe towards the opposite face of the posterior 

 lobe, as in the ordinary Kangaroo tj'pe of tooth, of which there is comjjaratively no 

 trace in the D. Australis. This tooth in the present species also differs in the 

 anterior basal ridge, being deeply indented in the middle by the posterior ridge of 

 the preceding tooth, and in the smaller development of the posterior basal ridge. — 

 Fifth or last molar (m. 3) : Antero-posterior length, including basal ridges, 2 inches 

 4 lines ; greatest transverse diameter, 1 inch 6 lines ; anterior basal ridge almost 

 obsolete; posterior basal ridge thick and strongly marked in the middle; antero- 

 posterior longitudinal ridge extending backwards from middle of posterior side of 

 anterior lobe nearly as in m. 2. Surface of all the molars longitudinally marked 

 with coarse, vermicular, reticulo-punctate, irregularly curved, wrinkles. 



As in South America the Geological period just before the 

 creation of man, had the gigantic Megatherium to prefigm-e the 

 little sloths of the present day, amongst the characteristic edentate 

 group of mammals of the Fauna of the same country ; so the little 

 native bears {Phascolarctos) of Victoria in our day, were preceded 

 at the same late Tertiary period of Geological time by equally 

 huge animals of their same genei'al marsuj^ial type, as characteristic 

 of the existing Australian Fauna, as the edentate is of that of South 

 America. The Diprotodon of Australia, curiously enough, like the 

 Megatherium of South American deposits, was obviously a feeder 

 on the twigs and foliage of trees, like their diminutive rejjresenta- 

 tives of modern times ; but in each case it was necessary to have 

 the same differences of conformation for the same reasons of the 

 enormous difference in bulk between the old genera and the new. 

 We have evidence in the ninth plate of this Decade that in the 

 Pliocene Tertiary times the so-called "Gum trees" {Eucalyptus) 

 were no larger in foliage or timber than now, and it is obvious that in 

 one case, as in the other, it would l)e impossible for gigantic brutes, 

 iiaving a body as bulky as that of a hippopotamus or rhinoceros, 

 to climb the trees, as the living American sloths or Victorian native 

 bears do, to get their food ; in each case, as the extinct forms 

 could not go up to the leaves, their powerful structure was so 

 modified that they could tear down the forest trees to feed on their 

 prostrate tops at leisure. No doubt this was done by both giants 

 much in the same way — the Megatherium and Diprotodon rising 

 on the hind legs, grasping the tree with the anterior limbs like a 



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