Mr. R. B. Sharpens Catalogue of Accipitres. 589 



diate between that which is usual in the bill of the white 

 Jerfalcon and the darker colour of the bill in the grey 

 races *. 



Of the younger liybrids (as I suppose them to be) to which 

 I have alluded^ one specimen^ said to be from Greenland, is 

 preserved in the Norwich Museum : in this Falcon the entire 

 plumage is that of a dark young bird of one of the grey races, 

 except the remiges and most of the coverts of the left wing, 

 the tertials of the right wing, the outermost rectrice on the 

 left side of the tail, and the four contiguous to it, all of which 

 resemble those of a lightly-marked H. candicans of similar 

 age ; in this bird the bill is darker than in Col. RadclifFe's 

 Falcon, and, in fact, does not differ from the usual coloration 

 observable in the bill of the Grey Falcons. 



The two similar specimens to which I have alluded are in 

 the collection of Mr. Hancock, who was so good as to allow 

 me to examine them when in Newcastle a few years since. 



According to a memorandum which I then made, one of 

 them has all the rectrices on the left side, except the last, 

 white, but with dark tips to two of them, and two similar 

 feathers on the right side of the tail ; it also has a feather 

 resembling the plumage of H. candicans amongst the scapu- 

 lars on the left side. The other one of these two Falcons is 

 a very dark young bird, in which the only indication of 

 hybridism is one primary resembling those of H. candicans. 



The following memoranda of measurements have been 

 taken from specimens in the British and Norwich Museums 

 and from others kindly lent to me by Lord Lilford, Mr. Han- 

 cock, and Mr. Dresser : — 



Grey Falcons obtained in Iceland. 



Tarsus. Middle toe s. u. 



Presumed males (four) . 



2-35 2-20 



2-20 2-15 



2-35 210 



2-50 210 



* Bills of an intermediate coloration, however, are not very unfrequent 

 iu specimens of H. candicans, especially in the more darkly-marked young 

 birds. 



