96 Prof. Owen on the Fossil Mammals of Australia. [Nov. 17, 



bearing of the characters of its mandible and dentition on the question of 

 the carnivority or herbivority of Thylacoleo is weighed. Alike comparison 

 and physiological consideration are applied to the mandibular characters of 

 Thylacoleo, Plagiaulax, and the true Rodentia in §12; and the author 

 next (§ 13) proceeds to the consideration of the form, structure, and 

 growth of the large incisors in the Diprodont paucidentate Marsupials, 

 and in the lemurine and lissencephalous Rodents. To the affirmation of 

 "the obviously phytophagous type of the incisors of Thylacoleo and 

 Plagiaulax " the author, referring to the descriptions and figures of those 

 teeth in the preceding part of his paper, enters upon a consideration of 

 the relations of their differences from those teeth in the truly phyto- 

 phagous Marsupials and Placentals to interrupted and continuous applica- 

 tion of teeth (§ 14). The alleged adaptability of the carnassials in Thyla- 

 coleo to reduction of vegetable food leads next to a consideration of the 

 work of the molar machinery in known existing Herbivora (§ 15). In 

 section 16 the place, and especially the family relations, of the Thy- 

 lacoleo in the Marsupial order are considered. Instances of existing di- 

 protodonts subsisting on animal food, and of existing polyprotodonts on 

 vegetable food, are adduced ; and, after comparisons with the genera 31a- 

 cropus, HalmaUirus, Lagorchestes, Heteropus, Petrogale, Osphranter, 

 Dendrolagus, Hypsijorymnus, Bettongia, Potorous, Dorcopsis, Cuscus, 

 Phascolarctos, Phalangista, Hepoona, Dactylopsila, Petaurus, Belideus, 

 Acrobata, Petaurista, JDromicia, Tarsipes, the author is led to assign 

 Plagiaulax and Thylacoleo to a distinct family of Diprotodont Marsupials 

 under the name " Paucidentata" in reference to the reduction of the molar 

 teeth to one on each side of the upper jaw, and two on each side of the 

 lower jaw. He then (in § 17) discusses the reality and value of the indica- 

 tions of tendency from the " general to the particular " in the dentition of 

 the mesozoic and neozoic Paucidentate Marsupials. The objections to the 

 predaceous nature of Thylacoleo and Plagiaulax from their alleged feeble- 

 ness and dwarfishness are discussed in § 18. The grounds on which John 

 Hunter was led to refer the molar of Mastodon ohioticus to either a carni- 

 vorous or a mixed-feeding animal, and those on which the author refers the 

 dentition and skull of Thylacoleo to a carnivorous species, are contrasted, 

 and the nature of a disparaging comparison is exposed in § 19. 



The author concludes by a description of certain unequal phalanges, 

 which supported a strong claw, bound close by a basal bony sheath, as in 

 the Lion, obtained from the breccia-caves of Wellington valley, and for 

 which, among the fossils thence exhumed, there is not, at present, any 

 other claimant save Thylacoleo. 



