52 Proceedings of the Royal Physical Society. 



Canada goose. The following are the particulars in which it 

 differs : — 



In colour. — In the Canada goose the white cravat does not 

 extend downwards along the under side of the neck, but is 

 quite abruptly defined, and cut off ; in B. leucolcema it does, so 

 as to give the appearance not only of a white cravat under 

 its chin, but also a white frill or shirt appearing in front down 

 its black waistcoat. In the Canada goose the white cravat is 

 flecked more or less with blackish specks ; in leucolcema it is 

 wholly white. In the Canada goose, the black head in front of, 

 and above the white cravat, is wholly black ; in leucolcema it is 

 flecked with an occasional white speck, and most so where it 

 joins the upper mandible both in front and on each side. In the 

 Canada goose the space between the rami of the lower man- 

 dible is black or blackish ; in leucolcema it is pure white. The 

 white on the lower eyelid is comparatively broad and distinct 

 in leucolcema; in the Canada goose it is a mere line like a 

 thread. 



The general tone of the plumage of the body, both above 

 and below, is considerably paler in leucolmma than in the 

 Canada goose — the black primaries having become brown, the 

 brown back having become somewhat fawn-coloured, and the 

 fawn-coloured under side having become dirty white, with a 

 pale bluish or lavender-coloured broad band stretching across 

 the belly between the two thighs. 



The black on the neck extends rather a shorter distance 

 down in leucolcema than in the Canada goose. 



The legs are yellowish-brown, and the interdigital spaces 

 bright yellow in leucolcema, instead of being black as in the 

 Canada goose. I believe that in some species of geese the 

 colour of the leg changes according to the age ; but this would 

 not appear to be the case in the Canada goose, because Cap- 

 tain Ord informs me that the colour is constantly black, 

 both in old birds and young broods, which he has reared since 

 1852. 



There are also some differences in the relative proportions, 

 which I shall tabulate for the sake of brevity and easier refe- 

 rence, and shall include in the comparison the proportions of 

 the following species supposed to be B. Hutchinsii. The mea- 



