144 Proceedings of the Royal Society of Victoria. 



But what name should be given to the species is a little doubt- 

 ful. Owen unhesitatingly referred his innominate, which came 

 from the Darling Downs, Queensland, to Palorchestes azael. But 

 Lydekker in his " Catalogue of the Fossil Mammalia in the 

 British Museum,"^ has declined to accept Owen's specific, or even 

 generic determination of the great series of Macropodid bones in 

 that collection. He says there is no reason why they should be 

 placed in one genus more than in another. Palorchestes was 

 founded on the characters of the skull, and at present there is no 

 evidence to correlate scattered skeleton bones, except their size. 

 Mr. Oldfield Thomas remarked during a discussion at the 

 Zoological Society that he found dimensions one of the most 

 useful characters in the identification of mammals. Hence there 

 is no reason to doubt that Owen was right in assigning his 

 innominate to Palorchestes rather than to Macropus, but as he 

 has himself- remarked some species of Procoptodon eg., P. goliah 

 (Owen) rivalled Palochertes in bulk ; hence size alone will not 

 help us to separate these two genera. 



The only evidence on this point is that of the teeth. A broken 

 tooth of the Fowler's Cove specimen was collected by Mr. Hall 

 and is now in the National Museum. Mr. Hall has identified it, 

 no doubt correctly, as a piece of lower incisor. It is 34 mm. 

 long, 16 mm. broad, and 7 mm. thick. In Procoptodon the lower 

 incisors are subcylindrical. They have, says Owen, " a full 

 elliptic section;" the diameters of the transverse section, 

 according to Owen's measurements, are 6 lines (12'75 mm.) 

 vertically, and 5 lines transversely. In Palorchestes on the 

 other hand the lower incisors are spatulate. Hence the evidence 

 of this tooth shows that the fossil cannot be a Procoptodon. It 

 is, therefore, in all probability, a Palorchestes azael, and justifies 

 Owen's idcHtification of the innominate figured by him in 1876. 



Accordingly the lower exposed part of the Sorrento dunes 

 dates back to the time of the extinct giant kangaroos, the age of 

 which is described as late Pliocene or lower Pleistocene, 



1 Pt. V. (1887), p. 239. 



2 Owen, op. cit., pt. ix. Phil. Trans., vol. clxiv. (1874), p. 800. 



