l^i HORN EXPEDITION SUMMARY. 



wliich may perhaps have entered somewhat hiter than the original polyprototlont 

 fauna. Their range on the continent was restricted as compared witli that of 

 other polyprotudonts and this, despite the fact thai they were, judged Ijy their 

 strength and ferocity, quite as well able to maintain a footing as their close allies 

 the species of Dasyurus. Possil)ly they owe their extinction on the mainland to 

 competition with the Dingo with whicli, being to a large extent arljorcal as well 

 as terrestrial, the Dasyurus did not enter into such close competition. 



The existing Diprotodonts we may divide into four groups : — 



(1). A widespread and presumably early developed series comprising represen- 

 tatives of the genus Macropus, Bettongia, Potorous, Dromicia,* Trichosurus and 

 Pseudochirus which we may regard as having been developed in the great centra! 

 area, and as having spread thence in all directions. 



(2). A series of forms also developed in the central area and confined to this 

 and the south-western parts of the continent. This includes representatives of 

 the genera Petrogale, Onychogale, Lagorchestes, Caloprynnius, Lagostrophus and 

 Tarsipes, some of which are now widely distributed over the area while others 

 are confined to one or more portions. 



(3). A series which may be regarded as having been developed in the sub- 

 tropical and tropical portions of the north and especially the north-east, and 

 comprising the genera Dorcopsis, Dendrolagus, Hypsiprymnodon, Disttechurus, 

 Phalanger, .^pyprymnus and probably Petaurus.f 



(4). A series which may be regarded as having been developed in the south- 

 eastern district including what is now the coastal parts of Southern New South 

 Wales, Victoi'ia, and also Tasmania, though the latter was separated off from the 

 mainland before the full development of these forms. This series comprises the 

 genera Acrobates, Gymnobelideus, Petauroides, Phascolarctos and Phascolomys. 



* It may be noted with re!,'ard to this genus tliat whilst it is an old form it is not restricted iti its distribution 

 to New Guinea, Western Australia and Tasmania, but certainly occurs on the mainland. Mr. Thomas, in the Brit. 

 Mus. Cat., 1888, ji. 14fi, st.ates in a footnote that he thinks it likely that the specimens of D. nnicolvr (= D. nana) 

 descriljed by Krefft as from the neighbourhood of Sydney, had escaped from capti\ ity. During the last few years 

 Mr. Dudley le Souef has captured D. nana at Genibrook in Gippsland, and a specimen of the same species h.as been 

 secured l)y myself on the Black Sjuir Range in Victoria and by Mr. A. Purdie at Sale, in Gijipsland. There is no 

 reason to thirds that these specimens have escaped from captivity. 



t This genus ought perhaps to be included in the next series, but its distribution over the northern )iarts of the 

 continent and in New Guinea, would seem to ally it rather with the north-eastern than witli the south-eastern series. 

 It is most strongly developed at the present day, in the coastal districts of New South Wales and Victoria, but is not 

 present in Tasmania (except as an introduced form). It was exidently one of the later developed arboreal diproto- 

 donts, as is shown by its absence from Tasmania. 



