371 
the Exploration of the Fly River. 
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 what 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 Ely River 
I found in the natives 5 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 been written when I received from Italy the descrip¬ 
tion of Tachyglossus {Echidna) bruijnii (W. Peters and Doria), founded 
on a portion of a skull found on the Arfak Mountains. 
