Systemat'ic Position of the Sheatk-bills. 1 35 



down feathers are conspicuous, but are somewhat degeneiate 

 in structure. As regards the vertex and occiput, they are 

 cliiefly disposed towards the sides, the mid-region of these 

 parts being occupied with preplumulse. The prepennse 

 extend forwards on the head to the supraocular region of 

 each side. Degenerate prepennae are seen on the chin and 

 below the malar region. A bare space (? colour in life) 

 surrounds the eye, and another bare space is to be noted 

 over the malar region. 



Bill hard and well-developed ; sheath ill -developed, 

 nearly concrete with rhamphotheca. 



Legs^feet, and claws extremely well-developed, and in size 

 appear to be out of proportion to apparent age of the bird ; 

 claws like the claws of an adult Grouse in point of strength 

 and development. 



This young bird is obviously older than it looks at first 

 sight, and the young of the Sheath-bills are evidently nidi- 

 colons. 



Adult Sheath-bills. — As is well known, the plumage of the 

 adult Sheath-bill is of uniform pure white colour, and the 

 general appearance of the bird is much like that of a 

 Ptarmigan. In the Ptarmigan and other x\rctic animals 

 the white (winter) plumage is, or has been, generally 

 regarded as procryptic and as affording protection from 

 enemies amidst a snow-covered environment. h\ the case 

 of the equally white Sheath-bill, it is interesting to reflect 

 that there are no birds of prey in the Antarctic Islands or 

 any carnivorous land animals. Indeed, from all accounts 

 the Sheath-bill itself is something of a bird-of-prey in a 

 small way. 



In Antarctic latitudes the chief " bullies " are the Skua 

 and the Albatros, more especially (as Mr. Ogilvie-Grant 

 informs me) il/acrowec/<?s [= Ossifraga). In connection with 

 this question of what possible use it can be for the Sheath- 

 bill to have a pure white plumage, Mr. Grant tells me 

 that Macronectes giganteus has two phases of plumage 

 coloration, a white phase and a dark grey phase, which 



