306 Prof. R. Owen on the Fossil Mammals of Australia. [Apr. 18, 



II. " On the Fossil Mammals of Australia. — Part VII. Genus 

 Phascolomys ; species exceeding the existing ones in size." By 

 Prof. R. Owen, F.R.S. Received March 25, 1872. 



(Abstract.) 



The author, referring to a former communication, in which the osteolo- 

 gical and dental characters of the existing kinds of Wombat were applied 

 in the determination of the fossil remains of extinct species resembling the 

 living ones in size, proceeds in the present paper to give the evidences 

 which have reached him of species of Phascolomys, formerly existing in 

 Australia, exceeding in size any that are now known to live there. 



The extinct species so reconstructed are described in the order in which 

 they progressively predominate in bulk over the existing Wombats. They 

 are referred to Phascolomys medius, Phascolomys magnus, and Phascolomys 

 gigas. 



The characters of these species are shown, not only by the size of ascer- 

 tained adult and aged individuals, but by modifications of shape of both 

 upper and lower jaws, and by differences of shape and of relative propor- 

 tion of certain teeth. Fossils exemplifying a moderate and seemingly de- 

 terminate range of variety in different individuals and probably different 

 sexes are noticed, and the evidences of some of these varieties of the 

 largest extinct species are figured. 



In his concluding remarks the author notices that, in the case of the 

 genus Phascolomys, as in that of other genera of which an adequate number 

 of fossil evidences have been acquired, the number of species which have 

 passed away exceeds that of the known living ones. 



Of the latter the growth of knowledge has been rapid and comparatively 

 recent, and all the species adhere to the size compatible with the burrow- 

 ing habits of the first observed Wombat (Phascolomys fossor, Wagner). 

 But a like habit and power of concealment cannot safely be ascribed to the 

 larger extinct Wombats. "If," remarks the author, "we knew the Hare 

 only by fossil remains, we should err in attributing to it the underground 

 retreat and way of life of the Rabbit." 



The evidence adduced in the present paper shows that all the larger 

 kinds of Wombat have perished. The author, in reference to the cause of 

 extirpation, refers to his remarks on the conditions affecting the contest for 

 existence, as applied to the larger extinct wingless birds of New Zealand, 

 and observes that the comparatively diminutive representative of Dinornis, 

 viz. the Apteryx, escapes pursuit and observation by being able to avail 

 itself, like the small existing Wombats, of an underground retreat. The 

 paper concludes with reference to the bearings of its subject on other 

 generalities. 



