FALGONIFORMES. 
all the forms are highly developed, and we find none that suggests a 
southern origin in any way, but all are readily placed as derivatives of 
northern stock. This would agree with the phylogeny of the group. 
Moreover, study of this group leads to the conclusion that there has 
been two distinct migrations from the north, and I will deal more fully 
with the particular instance of the two species of Haliastur. Thus, while we 
have specialised forms such as Circus assimilis^ Leucospiza, Erythrotriorchis, 
UroaetuSf Haliastur sphenurus, Lophoictinia, Gypoictinia, Notofalco, and 
Icracidca^ we have living alongside species apparently strictly referable to 
Circus, Accipiter, Hieraaetus, Butastur, Cuncuma, Haliastur indus, Milvus, 
Elanus, Baza, Falco, Rhynchodon, Cerchneis, and Paudion. These latter are 
all closely related to Indian, European or otherwise extra-limital forms with 
a wide distribution, and would appear to have arrived in Australia at a more 
recent date than the former. It might be argued that these might have 
arrived simultaneously, but being older forms have not been subject to 
variation to the extent of the species showing generic differentiation allied 
to endemism. I think this view is contradicted by the two species of 
Haliastur, and that this contradiction is confirmed by the Notofalco and 
leracidea. The fact that the New Zealand Hawk is also considered 
separable as Nesierax, and the nearest relative of this genus is at present 
supposed to be leracidea, I would cite as evidence of the descent of both 
from a northern ancestor. After much consideration I, however, conclude 
that a detailed examination of the osteology of all the species is necessary 
before conclusive speculation can be profitably indulged in. 
VOL. V. 
9 
