Two new species of Pimelodidae from Northwestern South America (Pisces, Nematognathi)

Since the publication of a paper on Auchenipteridae and Pimelodidae (Mees, 1974), I have received additional material of several of the genera there revised. This material includes a new species of Pseudopimelodus from Venezuela, increasing the number of species of that genus to six (two of which have several subspecies), and a new species of Microglanis from Ecuador, the eighth member of its genus. The main purpose of this paper is the description of these two new species. In addition, fresh material of Microglanis iheringi, a species of which previously I had examined only a single specimen, enabled me to supply some additional notes on it as well as an illustration showing its distinctive characters much better than do the photographs published by Gomes (1946: pl. 1), the only previous illustrations. For the loan or donation of specimens here discussed and for other valuable ichthyological material I am indebted to Dr. J. E. Böhlke and Dr. W. G. Saul (Academy of Natural Sciences, Philadelphia, U.S.A.), Dr. P. Cala (Dept. de Biología, Universidad Nacional de Colombia, Bogotá, Colombia) and Dr. D. C. Taphorn (Maracaibo, Venezuela). Pseudopimelodus apurensis species nova (pl. 1) Material. — One specimen, 11 February 1976, Río Arichuna (tributary of ApureOrinoco), near San Pedro, municipality of Rincón hondo, Apure, Venezuela (received from Dr. D. C. Taphorn, RMNH no. 27644), standard length ca. 290 mm, holotype. Diagnostic characters. — Even in its genus, consisting of heavy-bodied bottom dwellers, this species is distinguished by its large head and heavy body; the body is not so strongly tapering towards the tail as in other species; head and body not so depressed as in the other species with broad and heavy heads. Eyes small. Dentition in roof of mouth with large backward pro-