On the Affinities of the Falconidoe. 321 



to shew upon what ground our system of arrangement is 

 based. 



Characterising the genus Falco as we have restricted it, 

 we have the following characters.* Bill short, curved 

 from the base; cutting edge of upper mandible furnished 

 with a powerful tooth near its tip; cutting edge of under 

 mandible furnished with a notch corresponding to the tooth 

 in the upper. Tip of under mandible truncated perpen- 

 dicularly. Nostrils oval or rounded, and inserted into the 

 lateral part of the cere, which is broad and partially cover- 

 ed with feathers or naked. Gape reaching nearly as far as 

 the anterior angle of the eye. Plumage rather loose ; wings 

 long and pointed, reaching nearly to the tip of the tail; 

 inner web of first primary quill and external web of second 

 truncated, second primary quill longest, first and third 

 nearly of equal length, and about half an inch shorter, the 

 second and fourth much shorter. Tarsus of moderate length, 

 reticulated, upper part feathered anteriorly. Toes scutellated 

 and very long, the middle surpassing the external and 

 internal by one joint. Claws long, sharp, compressed late- 

 rally, and grooved below. Type, Falco communis, laniarius, 

 biarmicus, checquera, &c. Edinburgh Royal Museum. 



Differing from the above characters, we have the Falco 

 islandicus, forming, as already mentioned, the genus Hiero- 

 falco of Cuvier. In regard to this species there has been 

 much dispute, owing to the Baron Cuvier having given as 

 one of its principal characters, "bill furnished with a fes- 

 toon," which is met with in but few specimens. In all those 

 we have examined,f the bill was furnished with a powerful 



* Our characters have all been drawn up from specimens in different 

 collections which we shall refer to, for the information of others who 

 take an interest in this particular department. 



t In the Edinburgh Royal Museum these three specimens are adult 

 male and female, and a young bird of the second year. In Professor 

 Trail's collection there is a fine adult female. In the collection of the 

 Zoological Society of London, there are two specimens. 



