B K H J I LIPRARY MAR 1 8 1985 HARVARD useiini of Comparative Zoology us ISSN 0006 9698 Cambridge, Mass. 21 February 1979 Number 450 A NEW SPECIES OF MOENKHAUSIA FROM THE MATO GROSSO REGION OF BRAZIL (PISCES: CHARACIDAE) Wii.iiAM L. Fink' Absi R\t 1 . A new species of the characid fish genus Mofnkhausia is described trom the Arinos River of the Mato Grosso region of Brazil. A brief discussion of some of the characters used in analyses of characid relationships is included. INTRODUCTION The fish described here as new presents some interesting problems regarding current classification criteria for characids. These prob-lems arise primarily because the system now in use. which dates from the work of Eigenmann (1917). is obsolescent and no longer able to incorporate the diversity of the fishes it was intended to classify. Most of the characters which are used to "define" genera and higher categories have been found to be inadequate to express hypotheses about relationships within the family. The bases of the subfamilies Cheirodontinae and Tetragonopterinae have been re-cently reviewed by several authors (see Fink and Weitzman. 1974) and this critical reappraisal is being carried on in other areas within the Characidae. The characters which cause problems in hypothesizing the rela-tions of the fish herein described are lateral line length and color pattern. The former character is of major importance in the "Eigenmann" system while the latter has been virtually ignored by characid systematists. Both of these characters are discussed below after the description. 'Museum of Comparative Zoology. Harvard I'mversity. Cambridge. Mass. 02138.
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