1887. ] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 387 



offered, and that is, there are a great many species of Xorth American 

 birds which gradually increase in size as we pass from tlie southern 

 parts of the country in a northward direction. And liere we have it 

 very prettily exemplified in the skulls of the Eavens, for one specimen 

 comes from the southern limit of the United States and the other, and 

 at the same time the larger one, comes from the extreme northern 

 country— that is, from Alaska. 



FOET WiNGATE, NEW MEXICO, March, 1887. 



