PREFACE. 



The following paper is based largely on two collections of fishes, 

 the first being made by the writer and Mr. F. E. Lutz, of the Carnegie 

 Station for Experimental Evolution, Cold Spring Harbor, in the 

 spring of 1901, and the other by the writer during February, March, 

 April, and May, 1903. Through the courtesy of Dr. Barton W. 

 Evermann, assistant in charge of Scientific Inquiry, United States 

 Bureau of Fisheries, I have had at my disposal two small collections 

 made by Mr. E. W. Nelson, one from the Rio Balsas and the other 

 from the Rio Soto la Marina. Dr. W. L. Tower, of the University 

 of Chicago, also placed at my disposal a collection of fishes made by 

 him at Rio Verde, San Luis Potosi. In January, 1903, in Washing- 

 ton, D. C, Dr. Richard Rathbun, Assistant Secretary of the Smith- 

 sonian Institution, and Mr. B. A. Bean, Assistant Curator of fishes 

 U. S. National Museum, permitted me to examine a large collection 

 which formed a portion of the Mexican fish exhibit at the Columbian 

 Exposition. I have included only a small portion of this collection in 

 the following list because of the doubtful character of the localities 

 given. To have included the entire collection would have very much 

 confused our study of geographical distribution. 



An account of the collection made by Mr. F. E. Lutz and myself 

 is published in Vol. III. of the Zoological Series of the Field Colum- 

 bian Museum, Pub. 65, pages 63 to 128, plates 14 to 31. The results 

 of the second expedition are (1903) included in this paper. 



For assistance while making the collection of fishes in 1903, 1 wish, 

 on behalf of the Museum, to acknowledge my indebtedness to the 

 following gentlemen: Mr. C. R. Hudson and Mr. A. V. Temple, 

 of the Mexican Central R. R. ; Mr. D. W. Harvey, of the Mexican 

 R. R. ; Mr. R. B. Pegram, Mr. F. M. Ames, and Mr. A. Joy, 

 of the Vera Cruz & Pacific R. R. ; Mr. W. B. Ryan and Mr. 

 Newbury, of the Tehuantepec R. R. ; Mr. W. L. Morkil and 

 Mr. E. A. White, of the Interoceanic R. R. ; Mr. James Parkyn, 

 Treasurer of the Motzorongo Plantation; Gaham & Hudson, 

 Forlon, Tamaulipas; Mr. D. W. Hedrick, Superintendent of the 

 Midland Bridge Company; Mr . P. H. Kilpatrick, a contractor 

 on the Vera Cruz and Pacific R. R.; Mr. George Greenwood, 

 Superintendent of the Jalapa Electric Light Company; Mr. R. G. 

 Ransom, of the Westinghouse Air Brake Company; and the officials 

 of the Atchison, Topeka & Santa Fe R. R. I would especially men- 

 tion Mr. E. A. White for the personal interest he took in this work, 



