90 



FOSSIL MAMMALIA OF THE 



quadrate form, presenting four equidistant blunt tubercles, which are joined in pairs by 

 transverse ridges, but with these ridges less elevated than the points of the tubercles : there 



Fig. 10. 



Mandible and teeth, Dendrolagus dorcocephalus (nat. size). 



is a slight trace of the band of the tooth (' cingulum' of my " Odontography") "on the front 

 and back part of each molar, as in Macrojms. The hindermost molar is generally small, 

 almost round." ^ 



In those vegetable-eating Marsupials the molar teeth adapted to such diet are never 

 fewer and commonly more in number than in the most typical placental Herbivora. In 

 relation, apparently, with the drier and tougher vegetable fibres of Austraha, the premolar 

 is trenchant, and in the smaller Foeplto.ga is strengthened by vertical grooves and ridges. 

 In one of the New Guinea Tree-Kangaroos {Bendrolagus dorcocephahcs, fig. 10) this 

 trenchant tooth is proportionally larger than in the Australian Potoroos and Bettongs, 

 but the light-giving teeth — the true molars — are conformable with the macropode type.^ 



Fig. 11. 



FIG. 12. 



Mandible and mandibular teeth, \ nat. size, 

 Phascolarctos fuscus. 



Mandible and mandibular teeth, Plagiaulax (medius, mihi) Becklesii, 

 Falc, magn. 4 diam. (after Falconer).^ Reversed. 



A greater contrast in the Diprotodont series is seen in the mandible and mandibular 



teeth of the Koala [Phascolarctos, fig. 11) and Plagiaulax, fig. 12. 



' Waterhouse, " A Natural History of the Mammalia (Marsupialia),'" 8vo, 1845, p. 194. 

 - lb., p. 182, pi. 10, figs. 5, 5 a. 



3 ' Quarterly Journal of tlie Geol. See.,' vol. xiii (1857), p. 280, fig. 14; also ' Palaeontographical 

 Memoirs, &c.,' vol. ii, p. 41G, pi. 34, fig. 1. 



