VARIATION OF THE BEAN-GOOSE. 165 



curved ; average number of laminae along each edge of upper 

 mandible from 20 to 21, but sometimes as many as 24. As a 

 rule no white feathers at the base of the bill, excepting in old 

 birds, in which a small frontal patch of greyish white may occur. 



" Anser arvensis." — Bill : length of culmen rather over 

 2^- in., that is, approximately 63-64 mm. ; nail proportionately 

 small and rounded, included in the total length of culmen four 

 and a half times. " Orange colour extending nearly over the 

 whole of the upper mandible, having only a black bar com- 

 mencing in front of the nostrils and running along the culmen 

 to the base, where it becomes paler." Culmen straighter than 

 that of " segetum " ; average number of laminae about 28. A 

 conspicuous band of white feathers extending along the whole 

 basal edge of upper mandible. 



Mr. Frohawk thus bases the difference between his two species 

 principally on the following six points :■ — 



1. Different length of bill. 



2. Different proportions of the nail compared with the length 

 of culmen. 



3. Different degree of distribution of orange on the upper 

 mandible. 



4. Different number of laminse in the upper mandible. 



5. Absence or presence of a white feathered band along the 

 base of the upper mandible. 



6. Different upper outline of culmen. 



If we now proceed to make a comparison with the twelve 

 Swedish specimens of Bean-Geese shot during the spring migra- 

 tion near Upsala, it will be best to consider the different 

 characteristics one after the other. The first thing to do is 

 to arrange the birds in accordance with the length of their bills 

 (culmen), and to make the matter easier I propose to name the 

 specimens with letters a to m. The length of the culmen is then 

 in a=56, 6=57, c=58, d=59, e=59, /=61, #=62,* /i=62, 

 i=62, A;=63, Z=64, and m=68 mm. A considerable variation 

 is thus apparent. According to this measurement specimens 

 d and e should be " segetum " ; a, b, and c have a shorter 

 bill than the typical " segetum " ought to have ; a being even 

 almost as much shorter than the typical " segetum," as the latter 

 * g is the male and e the female of the same pair. 



