170 NATURAL HISTORY. 



teresting portion of the Grouse family. They live in the 

 far north in America and Europe. Their legs, and even 

 the feet, are covered with hair-like feathers. Their plu- 

 mage, like the fur of the Ermine and some other quadru- 

 peds, changes, as winter comes on, from a rich, almost 

 tortoise-shell color, to a pure white. The trade in Ptar- 

 migans in the north of Europe is very extensive. The 

 captured birds are kept in a frozen state for the dealers 

 who come for them. 



278. The Sheath-bills are a comparatively small family, 

 found chiefly in South America. Their nostrils are sur- 

 rounded by a kind of sheath, and their plumage is snowy 

 white. The Tinamous family, also a small one, is found 

 in the same country, where they seem to occupy the 

 same place that the Partridges and Quails do in other 

 countries. The family of Greatfoots is peculiar to Aus- 

 tralia and the adjacent islands. One of them is called 

 the Brush Turkey, from its resemblance in general form 

 to the common Turkey. It lives in the thick brushwood 

 of Australia. This and another bird, the Mound-making 

 Megapode (Greatfoot), are famous for making the mounds 

 spoken of in 205. This latter bird deposits its eggs 

 some five or six feet deep in its mound, and then covers 

 them up. Its mounds are very large. One of them was 

 found to be fifteen feet high and sixty feet in circumfer- 

 ence. They were at first supposed to be the tombs of 

 the aborigines. 



279. We come now to the order Cursores, or Runners 

 the Ostriches and their allies. We commonly think 

 of birds as being, of course, capable of flight, but here we 

 have a class of birds which are wholly terrestrial. Near- 

 ly all of them have wings, but all that their wings can do 

 is to assist them in running. Their wings being small, 

 the muscles which move them are small also. Accord- 

 ingly, the breast-bone is entirely destitute of the project- 

 ing keel ( 199) which it has in other birds, this being 

 needed only for the attachment of large muscles. In the 



