210 
Annals of the Transvaal Museum 
constant as group characters, that I cannot see why these should not be 
utilised for grouping purposes, even when superficially in structure species 
might seem to be allied. Difference in size may arise from conditions of 
climate, size of the prey, insular isolation or other local adaptation, the 
retention of a certain size being subsequently a matter of length of time 
under which the species may exist without the necessity of changing its 
environment or habits. Species found in the tropics are nearly always 
smaller than their allies found towards the poles and a recognition of this 
difference helps considerably towards a solution of the changes through 
which the species have passed, each physical change in the conditions of 
certain regions (which have undoubtedly taken place, as proved by 
palaeontology) effecting a change also in the fauna of those regions, which 
may give rise either to migration for part of the year, or local adaptation. 
To those who are perhaps sceptical, it would be best to refer to any large 
collection of these birds, where it will be seen that they form a most in- 
teresting study. 
Our Falco hiarmicus is obviously a southern representative of Hiero- 
falco candicans and for the present it might be very well retained in the 
same genus. Falco minor is likewise a southern representative of Rhyncho- 
donperegrinus, the smallest forms being found within the tropics, but these 
increasing in size again still farther south; Hartert has recently given 
dimensions of the tropical form as being those of minor, but the true minor 
of the Cape Province is a larger bird. According to Mathews {B. Australia, 
V. 221, 1915) the genotype of Falco is F, suhbuteo, a migratory species which 
occurs as such in South Africa. The resident representative of this species 
appears to me to be F. cuvieri A. Smith, which has, however, long ago lost 
the character of the heavy stripes below (being finely striped in immature 
only) and has the primary formula different; I propose for it the new 
generic name of Cuvieria. F. ruficollis is allied to Chiquera chicquera of 
southern Asia, and differs in having the underparts of the body more or 
less and the upper parts distinctly barred, and, like Cuvieria, differs from 
Falco in the wing formula. With regard to F. ruficollis, there seems to be 
general collusion to reject the name of F. horshrughi Gunning and Roberts 
(Ann. Transvaal Mus. in. no, 1911); but it may be pointed out that 
presuming the type and co-type are in immature plumage (despite the fact 
that they were breeding), the greater size of the birds admits of retention 
of the name in a subspecific sense at least. We have a male specimen of 
F. ruficollis from Damaraland (Finch-Davies), which is in the typical 
plumage marking of ruficollis, but rather larger and apparently much paler, 
as might be expected; and Mr A. K. Haagner has recently presented to the 
Transvaal Museum an adult female taken at Pyramids a few miles north 
of Pretoria, also with the plumage markings of ruficollis, but in size similar 
to the female of horshrughi. Having regard to the birds described as 
horshrughi coming so close to chicquera I think that it is still possible it 
may be a distinct species, the markings being so very different from those 
of ruficollis that the two might easily occur side by side and still not inter- 
breed. The matter is one which must, however, be settled by those who 
have more material for comparison. In the event of the type and co-type 
of horshrughi proving to be immature, the name will stand as a subspecies 
of ruficollis, while the pale bird from Damaraland, which is intermediate 
