HORN EXPEDITION — SUMMARY. 183 



However, wliether the e;ii'liest forms of true Diprotudoiits were devt'lupeil 

 within or outside of tlic limits of Australia we are probably safe in eoiicluding 

 tliat the eliaraeteristic ])iprotodonts of tlie region were developed in tlic great, 

 fertile eastern area of the interior and along the coast, and spread thence over the 

 continent, and noithwards into the Papuan region.* 



The larger forms now extinct, such as species of Diprotodon, Nototlierium, 

 Pliascolonus, Macropus, Protenmodon, etc., reached their greatest development in 

 Pliocene times and were characteristic of the eastern interior, spreading southwards 

 round the westi^in end of the Dividing Pange into Victoria. They do not seem 

 to have reached the eastern coastal district. 



In Post-Pliocene times, with the increasing desiccation of the whole central 

 aica they became extinct, though this extinction camiot be attributed wholly to 

 the drying up of the land, because in certain }>arts, such as Western Victoria, to 

 which they I'eacheil, the state of desiccation did not supervene ; but at the same 

 time it may perhaps be justly argued that the desiccation of the vast ;irea of the 

 interior was the largest factor in their extinction. 



Another fact may be noted with regard to this extinct fauna, and that is that 

 a,t the time of its development communication with Tasmania had apparently l^een 

 shut oil", at any rate no representative of this fauna reached the island, nor did the 

 Dingo, which appeared on the mainland prior to the final disappearance of thi; 

 large Diprotodontia., as its remains have been descriljcd by Sir F. McCoy as 

 occurring in Pliocene deposits at Colac in company with those of Diprotodon. 



yide by side probably with th(_^ sp(.'cia,lisation (jf the Diprotodonts the less 

 nioditieil Polyprotodonts were likewise giving rise to the existing tyjx'S, but 

 amongst them no such relatively gigantic forms were developed as amongst tin; 

 former. 



Perameles, Dasyurus, Phascologale and Sminthopsis sjiread widely over th<^ 

 whole of the continent from Tasmania in the south to New Guinea in the north, 

 and from the Indian coast on the west to the Paciiic coast on tlie east. Certain 

 f(jrms, however, such as Myrmecobius which may perhaps represent a primitive 

 antl little modified form, Peragale, Clueropus, Antechinomys, Da.syuroides and the 

 anomalous Notoryctes either not spreading beyond or being gradually contlned to 

 the drying uj) interior of the continent, whilst on the other hand Thylacinus and 

 iSarcophilus must be regarded as south-eastern forms, the immediate ancestors of 



* This oriniii of the true Diprotorloiitia on tlic oastcrn side of Anstrali;! wa-i sn;;;:esteil in tlie antlior's i)a,i)ei- 

 on "The Fauna anil Zoolouical Kelatinnships of Tasmania." Aust. Ass. Adv. Sci , vol. iv., Hobait, 1S!»2. 



