No. V.] 



ZOOLOGY. 



697 



M. Temminck has decided that the Larus Atricilloides of Falk is referable to this 

 species. 



Lestris Parasiticus. Arctic Lestris. 



Specimens in mature plumage, and with the under parts white, were brought 

 home by the Expedition. This species is subject to much variation of plumage in its 

 progress from youth to maturity; these changes are described, and the synonyms of 

 various authors enumerated, in Captain Sabine's Memoir on .the Birds of Greenland. 

 Individuals apparently perfectly mature, corresponding to the specimens now before us, 

 but having their under parts of a light brown, are frequently met with ; it is difficult to 

 account for this diversity of colour ; M. Temminck supposes that only the older birds 

 have white breasts, and that the darker hue of the under plumage is a proof of im- 

 maturity ; but the birds so marked are said to be found at the breeding-places, and 

 we know of no instance of such a marked difference between individuals of any spe- 

 cies of the same sex, and living in the same districts, which, have attained the age at 

 which they are capable of producing young. 



Anas. Swans. Geese. Ducks. 



Of this extensive genus, a very large portion are common to the Old and New 

 Worlds ; their power of flight renders their passage from America, and the lands of 

 the Polar Seas to the continent, and contiguous islands of Europe, easy. They come 

 in winter to these countries in quest of food, and return in spring to the more solitary 

 regions of the north, to rear their progeny. Some species, however, which are 

 inhabitants q# the north, do not migrate so far, and are confined to America alone. 

 The birds, which are common to the whole north, are so well known, and have been 

 so perfectly described by the various systematic writers, that an enumeration of the 

 names of the species will be a sufficient notice. Specimens of the following were 



• A. Fusca, - - - - - - Velvet Duck. 



A. Boschas, - - - - - Mallard, or, Wild Duck. 



A. Ferina, Pochard, or, Red-headed Wigeon. 



A Marila, ------ Scaup. 



' - A. Clypeata, - - - : - - Shoveller. ■: ' V .K 



A. Acuta, - - - - - - Pintail, or, Sea Pheasant. 



A. Grecca, - - - - - - Common or Green-winged Teal. 



• The following species, which are found in different parts of the northern hemi- 

 sphere, are not confined to America alone. 



A. Cygnus, - - - - - - Wild Swan. - 



; .• ..: A- Hyperborea, - U .-: Snow Goose. 



4 u 



