the Exploration of the Fly River. 371 



others immigrated from the nearest land, and especially from 

 Australia, and established themselves there, probably under- 

 going some modifications, but at all events retaining much 

 of the characters of the primitive type. And while the species 

 inhabiting the lowlands on both sides of the mountains differ 

 much, we find that those inhabiting the mountains are almost 

 invariably the same on both sides, no matter Avhat the dif- 

 ference of latitude or longitude may be. This may be ex- 

 plained ; for the alpine forms were not subjected to sensible 

 change of temperature, soil, &c., in their emigration, so long 

 as they kept to the mountains ; on the other hand, the forms 

 of the plain cannot cross the high mountains without mo- 

 dification. 



The geological union of Australia, the Aru Islands, and 

 New Guinea in a recent time is to me a certainty ; and I can- 

 not consider the granitic peaks of Torres Straits but as the 

 links of the chain which for a time joined Australia to 

 New Guinea. Mount-Ernest Island, The Brothers, and 

 Tawan Island, and all the other islands of Torres Straits, are 

 faithful witnesses to this. When the fauna and flora of New 

 Guinea and North Australia are better known and com- 

 pared, especially reptiles, small mammals, freshwater fish, and 

 other small animals of limited power for emigration, the fact 

 will be proved. Although I propose to confine myself to the 

 subject of birds, I cannot refrain from mentioning the existence 

 of an Echidna in New Guinea. Very far up the Fly River 

 I found in the natives' houses, carefully preserved, the quills 

 of an Echidna, and also many arrows whose barbs are made 

 with such quills. It is within my knowledge that the Rev. 

 Mr. Lawes obtained at Port Moresby a young animal from 

 the natives, which was described to me as like a Platypus ; 

 but I am inclined to believe it was a young Echidna"^. The 

 importance of such a discovery needs no comment. 



Among the Pigeon family I may mention Carpophaga spi- 

 lorrhoa, C. zoece, C. muellerii, Megoloprepia assimilis, Ptilo- 



* The above had beeu written when I received from Italy the descrip- 

 tion of Tachyglossus {Echicbia) bruijnii (W. Peters and Doria), founded 

 on a portion of a skull found on the Arfak Mountains. 



