264j Mr. Blackvvall on a ficxv Species of Hais^k. 



continually diminishing their capacities, notwithstanding the 

 nearly rigorous constancy of their tempei'ature, in order that 

 they should not cease to embrace their internal masses ex- 

 actly, the temperature of which diminishes sensibly. They 

 must therefore depart in a slight and progressive manner 

 from the spheroidal figure proper to them, and corresponding 

 to a maximum of capacity ; and the gradually increasing 

 tendency to revert to that figure, whether it acts alone, or 

 whether it combines with other internal causes of change 

 which the planets may contain, may, with great probability, 

 completely account for the ridges and protuberances which 

 have been suddenly formed at intervals on the external crust 

 of the earth, and probably also of all the other planets. 



XXXIII. On an undescribed Bhd of the Family Falconidse. 

 By John Blackwall, Bsq. F.L.S. Sfc* 



TOURING the last two years, five specimens of a minute 

 *-^ Hawk, no account of which, there is reason to believe, 

 has yet been published, have been brought to Manchester, at 

 different periods, from Brazil. On inspecting this new species, 

 it is evident from several peculiarities in its organization, that 

 it should occupy a situation, in a natural arrangement of birds, 

 intermediate between the Hawks and true Falcons; as it unites 

 in itself certain features characteristic of each of those groups. 

 Its short bill, curved from the base, the upper mandible of 

 which is furnished on each side with a small festoon ; the 

 shortness of its wings, notwithstanding the second quill-feather 

 is the longest, and the first has the inner web slightly emar- 

 ginated near its termination ; the moderate length of the tail 

 and legs ; the reticulated tarsi, and the acrotarsia feathered 

 from the knee to the middle, — plainly indicate that it must be 

 referred to the genus Gampsonyx, established by Mr. Vigors. 



Order. Raptor es. lUiger. 



Family. Falconidcc. Leach. 



Subfamily. Accipitrina. Vigors. 



Genus. Gampsonyx. Vigors. 



G. Holmii. The bill, which is much curved, is black faintly 

 tinged with blue. Plumage on the forehead and cheeks 

 pale orange; that on the top of the head, back, scapu- 

 lars and upper part of the wings, dark cinereous brown. 

 Greater wing-coverts and feathers of the spurious wings 



* Communicated by the Author. 



white 



