30 NORTHERN ZOOLOGY. 



DESCRIPTION 



Of an immature bird from Hudson's Bay, now in the British Museum. 



Colour of the head white, with longitudinal brown streaks. The feathers on the dorsal 

 aspect of the body have hair-brown centres, with white borders, and also an oval spot on each 

 web indented into the brown. The tail feathers have brown shafts ; in the two outer feathers 

 the brown encroaches on the webs, and in the two middle ones there are also six or seven 

 irregular brown blotches. The breast and belly have elliptical brown marks in the centres of 

 the feathers. In other respects, and in the acute tooth on the upper mandible, the spe- 

 cimen resembles the mature one above described. 



Dimensions. 



Inches. Lines. Inches. Lines. 



Length (total) . . . . 22 6 Length of the largest quill feather . .14 



,, of the tail . . . . 8 ,, of the tarsus . . .24 



The Falco sacer of Forster, sent from Hudson's Bay, and described in the 

 Philosophical Transactions, is a still younger bird than the preceding, probably a 

 yearling. 



Its upper plumage was dark brown, with pale reddish-brown margins and spots on the 

 webs, which did not reach the shafts. The quill feathers were brownish-black, with white 

 tips and edges, round rust-coloured spots on the outer webs, and transverse bars of the same 

 colour on the inner webs. The tail was dark brown, with a white tip, and crossed by about 

 twelve white bands. The head and whole under surface were white, with longitudinal brown 

 marks. Cere and feet bluish. Iris yellow. Its length was 22 inches ; its extent 36 inches, 

 and its weight 2\ lbs. 



The description of Edwards's Ash-coloured Buzzard corresponds nearly with Forster's, 

 but the colouring of his figure is indifferent. — R. 



The remarkable variation in the form of the bill, before alluded to, deserves 

 attention ; since naturalists have given no elucidation of a fact so curious. It has, 

 indeed, been surmised, that two species may possibly exist in our museums under 

 this name ; but on this point we can offer no opinion. Several instances, how- 

 ever, might be named, where the variation in the bills of individuals (unquestion- 

 ably of the same species) is fully as great as in the present instance. This fact 

 may be accounted for in two ways ; first, from the effect of age, the young not 

 having the full development of that structure which is typical of the adult ; thus, 

 in the youngest specimen of the American Harrier, subsequently described, the 

 cutting margin of the upper mandible is straight, while in the older specimens this 

 margin is strongly sinuated. Secondly, by that wonderful regularity in the progres- 

 sion of natural affinities, which is not only apparent in species, but even in the mode 

 of variation of those species. Sometimes these resemblances indicate analogies, 



