Douglas W. Nelson (UMMZ); Richard P. Van, Susan Jewett, Jeffrey T. Williams, 

 and Wayne C. Staraes (USNM); Hans Nijssen and I. J. H, Isbriicker (ZMA); and 

 J0rgen Nielsen (ZMUC). 



I am particularly grateful for hospitalities extended by the staffs of CAS, 

 USNM, AMNH, FMNH, MCZ, and MZUSP during my visits to their respective 

 institutions. ' : "" ■> 



For assistance in providing English translations of foreign literature I am 

 indebted to Horst O. Schwassmann, Dermis Haney, and Andrea Grosse. Horacio 

 Higuchi kindly provided me with a copy of Heraldo Britski's doctoral dissertation. 

 Carter R. Gilbert examined several critical type specimens in the collections at 

 Paris and Vienna. Walter W. Timmerman and Wendy B. Zomlefer provided 

 technical assistance in the preparation of several figures. James Clugston and 

 James D. Williams, U.S. Fish and Wildlife Service, generously permitted me to use 

 the laboratory facilities of the National Fishery Research Center in Gainesville. 



Aspects of this study benefitted greatly from discussions with Heraldo A. 

 Britski, Carl J. Ferraris, Jr., John G. Lundberg, Donald J. Stewart, Horacio Higuchi, 

 Alan H. Bombusch, John Friel, Mario C.C. de Pinna, Scott Schaeffer, Francisco 

 Provenzano, Antonio Machado-Allison, Ramiro Royero, Sven O. KuUander, Leo 

 G. Nico, Donald C. Taphorn, Lee Finley, Richard P. Vari, and others, particularly 

 participants of the 1988 catfish symposium at the annual conference of the 

 American Society of Ichthyologists and Herpetologists (ASIH) in Ann Arbor, 

 Michigan, and attendants of the 4th International Neotropical Freshwater Fishes 

 Symposium at the 1989 ASIH conference in San Francisco, California. 



I have benefitted immeasurably from the many fellow graduate students, 

 other colleagues, and friends who provided encouragement, constructive advice, 

 and companionship throughout my tenure as a graduate student. I would like to 

 express special additional thanks to the following individuals: Kevin Abbott, Gail 



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