THE THICK-BILLED GOOSE 



Melanonyx men talis, Oates 

 Plate 13 



Beloborody and Yaponsky gus (Buturlin) ; Klynvasty gus (Alpheraky). 

 English — The Thick-billed Goose, 



Anser mentalisy Oates, Man. Game Birds of India, ii. p. у у (1899). 



Anser {Melanonyx) mentalis, Buturlin, " Psovaya i Ruzh. Okh.," 1901 (Feb.-April) ; id., Dikie Gusi Ross. Imp., 



separ., 1 90 1. 

 Anser mentalis, Buturlin, Sinopt tabl. Okhotn. Pt. Ross. Imp., p. 42 (1901); Bianchi, Yezhegodnik Zool. Muz. 



Imp. Ak. N., 1902, vol. vii., No. 3, p. xvi. 

 Anser segetum middendorffii, Stejneger, Bull. U.S. Nat. Mus., No. 29 (1885), p. 142, pi. vii. fig. 1 (rostrum); 



(?) Nikolsky, Sakhalin i yego fauna, p. 224 (1889). 

 Anser grandis, Przewalski (nee Pallas), Mongoliya i strana Tangutov, ii. p. 150 (1876). 



Adult Birds 



Size very large. Plumage similar to that of M. segetum serrirostris or M. arvensis ; 

 the only specimen which I have been able to examine differing in nowise in colouring from 

 the large yellow-billed species. No white margin round base of upper mandible, but in 

 one example from Northern Manchuria (Inkow) a small light spot on very top of forehead. 



The main difference between this goose and the other representatives of the genus 

 Melanonyx consists in the extraordinary thickness or stoutness of the bill and in particular 

 of the lower mandible, so clearly shown in the plate of bills. 



In the original specimen which served Mr. Oates for the description of this goose 

 the whole chin was pure white; but neither in the example in the Zoological Museum at 

 St. Petersburg nor in a second from Bering Island, whose bill (under another name) is 

 figured by Mr. Stejneger, does the chin show any white. On this point I may note once 

 more that in two specimens of Melanonyx segetum brought in 1902 by Mr. Buturlin from 

 Kolguev, the chin has a large white patch, which clearly indicates the instability of this 

 character, and consequently its worthlessness for discriminating species. 



Total length $ (Bering Island) 

 Wing ...... 



Culmen ..... 



Bill from gape .... 



Depth of bill at base 



Greatest depth of lower mandible, visible with shut bill 



Tarsus ..... 



Median digit with claw 



Its claw ..... 



Number of teeth on each side of upper mandible, 20-25 (from three examples). 



130 



850 mm. (=33.40 in.). 

 495-497І mm. (= 19.40-19.50 in.). 

 69J-75 mm. ( = 2.73-2.95 in.). 

 71-72 ( = 2.79-2.83 in.). 

 40-4I7L mm. (= 1. 57-1. 63 in.). 

 13-15^ mm. ( = 0.51-0.61 in.). 

 96-100 mm. (= 377-3-93 in.). 

 93 mm. ( = 3.66 in.) (in one example). 

 15 mm. (=59 in.). 



