V i°s' X ] Allen, Origin and Distribution of N. A. Birds. IOs 



synopsis, subgenera will be in the main ignored, as their con- 

 sideration is found to rarely modify the results derived from a 

 consideration of the genera. Unless otherwise stated, the breed- 

 ing range alone is taken into account. 



The Pygopodes, as recognized in the A. O. U. Check-List, 

 consist of three families, Podicipidae, Urinatoridae, and Alcida?. 

 The Podicipida? constitute a small, well circumscribed group, of 

 almost universal distribution, and of great antiquity, dating at 

 least from the Miocene, with a closely related ancestral form in 

 the Eocene. The number of genera recognized varies from two 

 to half a dozen or more, according to the views of different sys- 

 tematists. Most of these so-called genera, however, are little 

 more than subgenera, and as such are geographically limited to 

 particular regions, some being tropical or austral, while others 

 are confined to the temperate portions of the northern hemisphere, 

 where they have a circumpolar distribution, as Colymbus and 

 Dytes of the North American fauna. yEchmophorus, scarcely 

 more than a well-defined subgenus, is confined to western tem- 

 perate North America, though allied to a connectent form 

 between y^Echmophorus and Colymbus in South America. It 

 is thus a distinctively American type. Podilymbtis, consisting 

 of a single species common to a large part of both North and 

 South America, is quite sharply separated from the other 

 members of the family, as a type peculiarly American, fossil 

 remains of which, according to Dr. Shufeldt, occur in the 

 Pliocene deposits of Oregon. 



The Loons, forming the family Urinatoridae, are distinctively 

 northern, and to a large degree arctic or subarctic, though some 

 of the species range in the breeding season throughout the cold 

 temperate latitudes. It is a compact, sharply defined group, 

 consisting of a single genus and less than half a dozen species ; 

 nearly all of them are circumboreal, none being distinctively 

 American. The Loons form one of the early types, having 

 survived with apparently little change from the close of the 

 Eocene. 



The Alcidoe, more numerous in genera and species than either 

 the Grebes or Loons, are, like the Loons, a strictly northern type, 

 several of the genera being among the most arctic of birds. With 

 a superficial resemblance to the Penguins of the antarctic seas, 

 but no close kinship, they may be regarded as their arctic repre- 



