1920] Swarth: Revision of Avian Genus Passerella 81 



the material thus assembled served to show the nature and extent of 

 the more important gaps still remaining, and requests were made for 

 the loan of skins from such museums as it was supposed might possess 

 the needed specimens. Here, again, the aid requested was most 

 cordially rendered. 



To each and all of the institutions and individuals who have aided 

 in the prosecution of this study by such loans I wish here to express 

 my gratitude for their generous help. The list of the institutions who 

 have thus contributed is as follows: American Museum of Natural 

 History, New York ; California Academy of Sciences, San Francisco ; 

 Carnegie Museum, Pittsburgh; Field Museum of Natural History, 

 Chicago; Museum of History, Science and Art, Los Angeles, Califor- 

 nia; Provincial Museum, Victoria, British Columbia; University of 

 Kansas Museum, Lawrence, Kansas ; United States Biological Survey ; 

 United States National Museum ; Victoria Memorial Museum, Ottawa, 

 Canada. Private collectors to whom similar acknowledgment is due 

 for the loan of specimens are as follows : L. B. Bishop, Allan Brooks, 

 F. S. Daggett, W. L. Dawson, D. R. Dickey, W. 0. Emerson, J. H. 

 Fleming, J. Grinnell, A. B. Howell, S. G. Jewett, C. Lamb, J. E. Law, 

 John W. Mailliard and Joseph Mailliard, L. H. Miller, G. F. Morcom, 

 J. A. Munro, J. R. Pemberton, W. M. Pierce, C. H. Richardson, F. J. 

 Smith, A. Wetmore, G. Willett, L. E. Wyman. A small series from 

 the writer's private collection was also available. The total material 

 assembled from the above sources was approximately 1800 specimens. 

 The writer was enabled to examine the type specimens of fourteen 

 of the sixteen subspecies here recognized, that is of all save iliaca and 

 unalaschcensis, which are presumably non-existent. 



It seemed advisable to list every specimen examined, and this 

 accordingly has been done, with entry of such data as appeared essen- 

 tial. "Where quotation marks are used the items thus enclosed are 

 copied verbatim from the labels ; this usage is followed, as a rule, 

 where the facts are obscure. In these birds variation is so extensive 

 and of such a nature that not only might different people arrive at 

 different conclusions after study of the same material, but the same 

 person might handle certain skins at different times and label them 

 differently each time. The habit of migration in Passerella adds a 

 further complication in the classification of individual specimens taken 

 at points other than the summer home, giving rise to difficulties such 

 as are summarily dismissed in the case of similarl}^ variable but 

 non-migratory species. 



