Eastern Bean-Goose 



i*5 



other dimensions and the structure of the bill, and it cannot in any wise be regarded as a 

 decisive and important character. As we have already seen when describing the typical bean- 

 goose, the bill, with a oilmen-length never exceeding 62 mm. ( = 244 in.), 1 has a greatest 

 depth of the visible part of the lower mandible (with shut bill) of from 7І to 9.2 mm. 

 ( = 0.29—0.36 in.). The bill of the Siberian form {M. segetum serrirostris), on the other 

 hand, varies in length between 62 and 72 mm. ( = 2.44—2.83 in.), and has a maximum depth 

 of lower mandible, under like conditions, of from 10 to 12 mm. ( = 0.39—0.47 in.), but 

 oftener between 11 and 12. 



As in the typical M. segetum, so in the race now described, the number of teeth on 

 each side of the upper mandible usually varies from 20 to 21 ; and I once thought that this 

 was the limit, but, as we shall see at the end of this notice, this number is sometimes increased 

 to 25, so that in this case also I am confirmed in my view that the number of teeth in this 

 group of geese is not constant. 



Although the arrangement of the black and light areas on the bill is absolutely the 

 same as in the typical form, I have not seen in M. segetum serrirostris the colouring 

 extending backwards beyond the anterior margins of the nasal depressions, which occasion- 

 ally happens in the typical bean-goose. With the exception of this light ring, embracing 

 both mandibles in the apical part, the whole bill is black. 



Plate 23 shows clearly the difference in size and stoutness of the bills of both forms 

 of this goose, while below are figured side by side the upper mandibles of both. This 



M. segetum, £ 



Culmen 59I mm. 



(Europe.) 



M. segetum serrirostris, <$ 



Culmen 69 mm. 



(East Siberia.) 



M. segetum mentalis (?!). 

 Culmen 72 mm. 

 Japan (Brit. Mus.). 



Type. 



comparison is necessary, because M. mentalis has a bill closely resembling in structure those 

 of the other two bean-geese ; and in all probability that form will prove to be nothing more 

 than a large type of M. segetum serrirostris, as is mentioned in the sequel. 



1 I have not myself seen an example with culmen exceeding 61 mm. ( = 2.40 in.); but as Dr. Madarasz speaks of one with 

 62 mm. ( = 2.44 in.), I think this size may have been the result of measuring the bill along the arc, and not the chord as I have 

 always done. 



