Yellow-billed Bean-Goose 99 



The nasal depressions in the yellow-billed goose are in the form of a very elongated 

 oval. The oblong nasal aperture lies in the foremost end of the nasal depression, reaching 

 with its anterior edge almost to the middle of the bill. 1 The nares are pervious, but only 

 in their rounded posterior portion. The greatest depth of the part of the lower mandible 

 visible laterally with shut bill very seldom exceeds 8 mm. (=1.31 in.), and only in one 

 Turkestan example with culmen 72 mm. ( = 2.83 in.) does it attain 8| mm. ( = 0.33 in.). 



The number of teeth on each side of the upper mandible varies usually between 25 

 and 28, but in rarer cases there are 24, and from information I have received in one 

 individual there were only 23. 



At first I attached great importance to the number of teeth for the determination of 

 species, but have now been obliged to change my view on this character, as specimens 

 received in 1902 by Mr. Buturlin from Novaia Zemlia and Kolguev, as also others kindly 

 examined for me by Mr. Frohawk, clearly showed that the number of teeth is not always 

 a trustworthy character. Indeed, in the majority of specimens of M. segetum examined by 

 myself there were only 20 to 21 teeth, but I have now in my hands bean-geese from 

 Kolguev with 24 and 25 teeth. It seems therefore that, in some geese, the number 

 of teeth slightly increases with age, or, more exactly, certain teeth in younger birds are very 

 feebly developed, and only with maturity attain their full size and become conspicuous. 



Injuries to the bill are far from rare in geese, and probably mostly occur in early 

 youth. As a rule, on finding in skins that the bill has been injured, one may confidently 

 conclude that the number of teeth will be abnormal. 



In M. arvensis (as in other representatives of the genus) along the edges of the lower 

 mandible are 9 or 10 more teeth than in the upper, so that if, for example, there are 26 teeth 

 on each side of the upper mandible, one may almost certainly say that in the lower there 

 will be from 35 to 36. The comparative depth of the lower mandible greatly simplifies the 

 distinction of the yellow-bill from the bean-goose at any age, and that, too, alike in fresh- 

 shot individuals or dry skins. 



Turning to the colouring of the bill and noting the most essential points relating to 

 M. arvensis, we find that in perfectly adult birds of both sexes the bill is almost wholly 

 yellow-orange ; and only occasionally is this colouring replaced in the basal half of the bill by 

 a light rosy flesh-tint, which can be seen only in fresh-killed birds. In dry skins all the 

 light parts of the bill are wholly yellow, orange, or reddish orange. 



The nails of both mandibles, as in all the representatives of the genus Melanonyx, 

 are wholly black and glossy, and the teeth for the most part of a dark colour, and not 

 whitish, as in the species of the genus Anser. Again, the black colouring on the culmen 

 itself, between the nares, extending anteriorly approximately to the line uniting the fore- 

 edges of the nares, rarely reaches farther towards the apex. This black colouring on 

 the culmen sometimes reaches to the feathering of the forehead, but more often falls short 

 by a few millimetres. Ordinarily there is a black stripe on the sides of the base of the upper 

 mandible, either in contact with the feathering of the head or slightly removed from and 

 parallel to the same. 



In very old birds, in which the white feathering at the base of the upper mandible is 

 already absent, sometimes the whole upper mandible,, with the exception of the black nail 



1 I note here by the way that in Khomyakov's representation of the bills of geese in his Ptitsy Ryazanskoi gub., pi. ii. ff. i and 3, the 

 nasal apertures are brought too near to the apex of the bill, which is not the case in the originals, as I convinced myself when examining 

 them. 



