PROC. BIOL. SOC. WASH. 100(3), 1987, pp. 640-652 TWO NEW SPECIES AND A NEW GENUS OF MINIATURE CHARACID FISHES (TELEOSTEI: CHARACIFORMES) FROM NORTHERN SOUTH AMERICA Stanley H. Weitzman and Richard P. Vari Abstract. —The first known miniature characid fishes apparently aligned with the Characinae and Cynopotaminae are described as new fi-om the Rio Negro and Rio Orinoco drainages of Venezuela and tributaries of the Rio Amazonas in Colombia. Although the suggested relationships of the new genus {Priocha-rax) and species {P. ariel and P. pygmaeus) to those subfamilies appear rea-sonable, their exact phylogenetic relationships within the Characinae and Cy-nopotaminae remain obscure. The new species are distinguished from others in these subfamilies primarily by a higher number of jaw teeth, a lower number of pelvic-and anal-fin rays, retention of larval pectoral fins in adults, and a minute adult body size of a maximum of about 1 7 mm in standard length. The early explorer-naturalists who sam-pled the South American freshwater fish fauna focused nearly exclusively on species of moderate to large body size, evidently under the mistaken belief that all smaller fishes were juveniles, or if distinct the species were unimportant. Agassiz, during the Thayer Expedition to Brazil in 1865, was the first collector who fully endeavored to collect even the smallest fishes, recognizing that such specimens often represented in-teresting species of small adult size. During the twelve decades that have passed since that trip numerous species of relatively small adult body sizes have been described from the freshwaters of South America. Recent collecting efforts in Venezuela have yielded miniature species of the family Lebiasinidae (Fernandez and Weitzman 1987) and the subfamily Characidiinae of the Characidae (Weitzman 1986). Those collections also re-vealed the existence of a miniature species evidently aligned phyletically with the char-acid subfamilies Characiinae and Cynopo-taminae. A second, very similar species, originally collected in the Colombian Am-azon, was subsequently found in the collec-tion of the Naturhistoriska Riksmuseet, Stockholm. These two species, assigned herein to a new genus, are described as new and the possible phylogenetic relationships of these taxa are discussed. Methods and Materials The counts and measurements are those described by Fink and Weitzman (1974:1-2). All measurements other than standard length (SL) are expressed as a percentage of SL except subunits of the head which are expressed as a percentage of head length or as otherwise noted. Specimens examined for this study are deposited in the American Museum of Nat-ural History, New York (AMNH); Acade-my of Natural Sciences of Philadelphia (ANSP); British Museum (Natural History), London (BMNH); California Academy of Sciences, San Francisco (CAS); Field Mu-seum of Natural History, Chicago (FMNH); Museo de Biologia, Universidad Central de Venezuela, Caracas (MBUCV); Museu de Ciencias, Pontificia Universidade Catolica do Rio Grande do Sul, Porto Alegre (MCP);
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