SUB-FAMILY ATHBNISA 
G-ENUS MICRATHENE. 
Micrathene. Coues. P. A. N. S. (18G6.) p. 51. 
40. MICRATHENE AYHITNEYI. Yol. I. Plate XXIX. 
EMILY II — FALCOYIDiE. 
SUB-FAMILY FALCONINzE. 
GENUS FALCO. 
Fcdco. Linn. Sysf. Fat. Yol I. (17G6.) p. 124. 
41. 
FALCO CANDICANS. 
A r ol. II. 
Plate XXX. 
42. 
— ISLANDICUS. 
Yol. II. 
Plate XXXI. 
43. 
— AURANTIUS. 
AMI. II. 
Plate XXXII. 
SUB-FAMILY ACCIPITRINiE. 
GENUS ACCIPITER, 
Accipiter. Briss. Ornitli. (17G0). Yol. Ip. 310. 
44. ACCIPITER MEXICANUS=A. COOPERI. 
Accipiter Mexicaxus. Swain’s Faun. Bor. Am. p. 45. 
Mr. Cassia has designated the three members which constitute this genus in North America, as “A group in which size is a specific 
character.” As nothing is so liable to mislead an ornithologist in his investigation of species, as the variation in measurement of his 
examples, it seems most unwise to establish a species whose only qualification is size. Particularly does this objection appeal with force, 
when it is applied to the great family of hawks, whose members are notorious for variations in size. I have examined carefully specimens 
of acknowledged A. Mexicanus, and compared them with those of A. Coopcri, and they appear evidently to belong to one and the same 
species. 
It is impossible to define characters which would enable the two birds to be distinguished from each other. 
SUB-FAMILY BUTEONINkG. 
G-ENUS BUTEO. 
Buteo. Guv. Anatom. Cornparee. (1799). 
45. BUTEO MONTAN US B. BOREALIS. 
Buteo Montanus. Nutt. Man. Ornith. Yol. I. (1840). p. 112. 
This is the western representative of B. Borealis, or is generally so considered, and it might be deemed a local race if a distinct 
range of locality could be assigned to it. The finest specimen I ever Saw, was killed at Carlisle, Pennsylvania, and is now, or was when 
I saw it, in the collection ol the Smithsonian Institution, proving that this form is not exclusively western. The specimens from the west 
of the Rocky Mountains appear to be slightly larger than are those from the eastern part of the continent, but examples constantly occur 
there which cannot be recognized from the common species of the Atlantic States. The variations among individuals belonging to Buteo 
Borealis both in color of plumage and measurement of their parts, arc so great and extensive, that to admit the style called B. Montanus 
to specific rank, would of necessity entail the acknowledgment of many more forms to the same privilege, as is very conclusively proved 
by Dr. Bryant in his able paper upon “ The variations in Plumage of B. Borealis and B. Harlani,” published in the Proceedings of the 
Boston Natural History Society, ( 1861) p. 107. And as these different forms appear not to be restricted to any particular section of 
country, for many a western “Red-tail” is identical with eastern examples, nor to vary in any way that is peculiar to themselves as a 
class, it would seem the far more reasonable conclusion to consider them as all members of one species, until further information could 
prove that such decision was incorrect. 
46. BUTEO ZONOCERCUS. Yol. II. Plate XXXIII. 
SUB-FAMILY AQUILINzE. 
GENUS HALIzETUS. 
Halketus. Savig . Descrip . de V Egypt. Zool. p. 85, 
47. HALLETUS PELAGICUS. Vol. II. Plate XXXIY. 
48. — ALBICILLA. Yol. II. Plate XXXY. 
