ORNITHOLOGICAL EXPLORATIONS. 237 



notes," fascinatiug the listener by the cheerfulness if not by tlie beauty 

 of their music, notwithstanding the 5 to 6 feet depth of snow on the 

 ground. 



As already stated, the lark occurs also on Bering Island, where a 

 few may be heard during the summer between the village and Ladi- 

 ginsk, among the sand dunes covered with a luxuriant growth of 

 Elymus. 



Family COEVID^. 



106. Corvus behringianus (Dyb.). 



1826. — Corvus corax Pall., Zoogr. Rosh. As., I, p. 380 (part). 



1883. — Corvus corax behringianus Dybowski, Bull. Soc. Zool. France, 1883, p. 363. 



1884. — Corvus grebnitskii Stejneger, Pr. Biol. Soc. Washiugt., II, p. 97. 



I have not been able to detect any difference between my specimens 

 and those from Central Europe in respect to dimensions, size, or shape 

 of the bill, size of the nasal bristles, or luster of the plumage. 



The only distinction I can see is the different wing formula, which in 

 all specimens examined by me is constant. Going over the literature, 

 besides, I find it unanimously stated that in the European bird the 

 third and the fourth primaries are the longest, the third being decidedly 

 longer than the fifth, while in all my ravens from the Commander 

 Islands the fourth and the fifth are the longest, the latter being a trifle 

 shorter than the former, but considerably longer than the third, the 

 difference in the two forms consequently being very well marked. At 

 the same time the first primary seems to be reduced in length, as it falls 

 between the eighth and the ninth, in one instance even between the 

 ninth and tenth, while I think the rule in the European species is that 

 it falls between the seventh and the eighth. 



These differences may have originated in the insular habitat of the 

 present form, but wViatever may have been the cause, the difference is 

 now established ; and it does not invalidate the distinctness of the form 

 that we are able to point out its probable cause. If the suggested 

 explanation be true, it would be a most remarkable fact, showing the 

 effect of insular isolation even on so powerful a flyer as the raven. As 

 we here have a case of " breeding in and in" within a small stock, it is 

 interesting to observe that it has not had the same influence as on the 

 Foer Islands, where it seems to have produced a race of partial albinos. 



A comparison with the large series of skins of C. corax carnivorus 

 from North America, especially with those from Alaska, has not been 

 neglected, the result being that the Commander Islands birds are distin- 



