24 THE CHICAGO ACADEMY OF SCIENCES. 



late migrants, or those which do not intend to nest in the north 

 it seems difficult to state. 



CLASSIFICATION. 



The classification adopted for this catalogue is that of the 

 American Ornithologists' Union Check-list, with such additions 

 and corrections as have been published from time to time in the 

 "Auk." My thanks are due to Mr. J. A. Allen, Curator of the 

 Department of Mammalogy and Ornithology of the American 

 Museum of Natural History, New York City, for assistance in 

 correcting the classification of certain species. 



Mr. Robert Ridgway's magnificent work on the Birds of 

 North and Middle America has not been available as a basis for 

 classification as its publication is unfinished; and also for the 

 reason that the sweeping changes in nomenclature in that monu- 

 mental work might lessen the value of a purely local catalogue. 

 A number of changes in specific and generic names, however, 

 have been adopted from Mr. Ridgway's work. 



