368 ON THE GENUS MICRASTUR. [May 27, 
but we have hitherto wrongly referred it to its southern representa- 
tive M. gilvicollis, in which other authors have followed us. In its 
plumage above, this present bird very much resembles that species ; 
but beneath the narrow grey bands are closer together, and are con- 
tinued regularly over the thighs, belly, and crissum, whereas in M. 
gilvicollis they gradually disappear, leaving these parts nearly white. 
In the adult of M. guerilla also there appear to be three distinct 
white tail-bands besides the narrow terminal band; in the adult M. 
concentricus the normal number seems to be one, or sometimes two. 
Cassin founded his Micrastur guerilla upon immature specimens 
obtained by Mr. Pease near Jalapa in Mexico, and has figured the 
bird in this plumage. As already stated, we have seen other ex- 
amples in the numerous collections recently made in the same dis- 
trict. In Guatemala Salvin found it common in all the low- 
lands of the Atlantic slope. From Veragua Arcé has transmitted 
individuals both in the adult and immature plumages. We have not 
yet seen it from Panama; but it certainly extends as far south as 
Western Ecuador, where Mr. Fraser obtained an adult specimen in 
1859. This bird is now in the collection of Salvin and Godman. 
7. MiIcRASTUR GILVICOLLS. 
Sparvius gilvicollis, Vieill. N. D. x. p. 323, et Enc. Méth. p. 1264 ; 
Puch. Rev. Zool. 1850, p. 91. 
Micrastur gilvicollis, jr., Pelz. Orn. Novara, p. 10, et Orn. Bras. 
p- 7; Sel. et Salv P. Z. S. 1867, p. 590. 
Nisus concentricus, Less. Tr. d’Orn. p. 60 ; D’Orb. Voy. Ois. p. 88. 
Climacocercus concentricus, Cab. in Tsch. F. P. pp. 18, 98, et in 
Schomb. Guian. iii. p. 735; Burm. Syst. Ueb. ii. p. 87. 
Hab. Cayenne (Less.) ; Eastern Peru(Tsch.) ; Bolivia (D’ Orb.) ; 
Rio Negro, Barra and Para (Natt.). 
Vieillot’s Sparvius gilvicollis was founded upon a specimen in the 
Paris Museum, which Pucheran, in one of his articles upon Vieillot’s 
types, declares to be the same as M. concentricus. Now, although 
Falco concentricus is an old MS. name of Illiger’s, it was first pub- 
lished by Lesson, and based upon a specimen brought by Poiteau 
from Cayenne, likewise in the Paris Museum. It follows that M. 
Pucheran, having had the two types before him, had an excellent 
opportunity of arriving at the result which he came to. 
Our worthy friend Herr von Pelzeln, of Vienna, has, however, 
recently come to a different conclusion, and, in his treatise on the 
birds of the Novara Expedition, has treated M. gilvicollis and M. 
concentricus as different species. This caused us no small perplexity, 
until, with his usual kindness, Herr v. Pelzeln transmitted to us for 
examination the whole series of specimens of these two supposed 
species upon which he had founded his remarks. We trust that our 
good friend will pardon us, if, in the interests of science, we state that, 
after inspection of the specimens and comparison of them with others 
now before us, we have arrived at a somewhat different conclusion. 
It is certain that the bird from Mato Grosso, which Herr v. Pelzeln 
regards as the adult of his M. gilvicollis, is distinct from his M. con- 
