148 Mr. 0. Salvin on the Genus Geothlypis, 



America G. poliocephala. We now find that, in addition to these, 

 another race exists in Chiriqui, which is almost as distinct from 

 the others as they are from one another. 



An examination of an extensive series of the better-known races 

 just mentioned shows that they possess, as pointed out by Baii'd, 

 distinguishable characters ; and this I take to be sufficient justifi- 

 cation for separating them under different names. Our Chiriqui 

 specimen is unfortunately unique ; but the relationship it bears to 

 the other races of the same stock is such that it cannot well be 

 classed with any of them without involving the removal of the 

 barriers which have reasonably been shown to exist between them. 

 In other words, we should have to call G. velata, and perhaps also 

 G. poliocephala, "varieties" of G. aquinoctialis ; and this I am 

 not prepared to do, seeing that the variation is associated with a 

 law of geographical distribution, and therefore indicates some- 

 thing in advance of individual variation, to which alone, in my 

 opinion, the term "variety" can properly be applied. Then, too, 

 the fact of the Chiriqui bird being somewhat more closely related 

 to the Brazilian race than to any of the othei's, singular as it may 

 at first sight seem, is in strict conformity with other instances of 

 a similar distribution in other allied forms, not only of birds, but 

 also of other animals. The science of geographical distribution 

 demands that all such cases should receive close investigation. 



Our single specimen, which I propose to call Geothlypis 

 CHiRiQUENSis, is a male in adult plumage, and differs from an 

 equally adult example of the same sex, from Costa Rica, which I 

 have attributed to G. poliocephala, Baird, /. c* (cf. Ibis, 1870, 

 p. 114). In this last-mentioned bird the whole hind parts of the 

 head and nape are ashy, the black of the loral region extending 

 in a narrow line over the forehead and under the orbit as far as 

 its posterior margin. The ear-coverts are ashy, and the flanks 

 tinged with ochraceous brown. In the Chiriqui bird the ash- 

 colour of the head is more restricted, and does not extend over 



* Baird described this species from a Mazatlan skin, and states that a 

 Guatemalan skin I sent him differed somewhat, and especially in the 

 former having white eyelids. In the specimens we possess the eyelids 

 are not white ; but some have a few white feathers ; so that it is probable 

 that the character is not a stable one. 



