BEAN-GEESE OF ASIA. 561 



long , depth of bill 1-31— 1-41 in., rarely 



1 -46 in. ; depth of lower mandible 0-39 — 



0-47 in,, less commonly down to 0*37 or in 



young ones to 0*35 in. and up to 0*49 in. ; 



wing 16-3 — 19-2 in. long (straight from 



corpal joint to end) serrirostris Swinh. 



f 1 . Pale colouring of the bill extends — at 



least in adults— far back under the 



nostrils ; exposed culmen about 2*82 — 



2-95 in., sometimes down to 2 - 73 in. long ; 



depth of bill 1*5 — 1-63 in., sometimes 



down to 1*42 in. ; depth of lower mandible 



0'51 — 0-61 in., sometimes 0*47 in. ; (wing 



19-48 — 19*60 in., sometimes down to 19-0 



in. long) mentalis Oates. 



Among these birds Anser (or more precisely Melanonyx) brachyrhynchus, A. 

 neglectus. A. arvensis and A. segetum are perfectly "good" species, but A. 

 sibiricus is only an eastern sub-species of A. arvensis, and A . cameirostris. A. 

 serrirostris and A. menial is are geographical forms or sub-species of A. segetum. 



