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 (' cingulura' of my "Odontography") "on the front 

 airtl back part of each molar, as in Macrojjus. 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 Ilerbimra. In 

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

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

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

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

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



Fig. II. 



riG. 12. 



Mandible and inandilmhr tpoth, 

 Phascolarclos fiiscus. 



Mandible and mandibular teeth, Plagiaulax (medius, mibi) Becilesii, 

 Falc, niagn. 4 diam. (after Falconer).-' Reversed. 



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

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



' Wateriiouse, "A Natural History of the Mammalia {Marsupialia}," 8vo, 1S45, p. 194. 



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



s 'Quarterly Jourual of the Geol. Sec.,' vol. xiii (1857), p. 280, fig. 14; also ' Palseoutographical 

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



