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Show 1868.] DR. A. GUNTHER ON NEW AMERICAN FISHES. 229 5. Descriptions of Freshwater Fishes from Surinam and Brazil. By Dr. A L B E R T G U N T H E R , F.R.S., F.Z.S., & c (Plates XX., XXL, XXII.) The British Museum received in the course of last year several collections of freshwater fishes from Surinam and Brazil. Whilst engaged in the determination and arrangement of these examples, I have found several species which do not appear to have been described hitherto. All of them belong to the Siluridce and Chara-cinidce. The collections whence these examples were obtained are the following:- I. A collection made by Mr. Edward Bartlett on the Huallaga, a tributary of the Upper Amazons, and on a smaller tributary near the town of Xeberos. This collection contained a greater proportion of new species than one made by Mr. Bartlett on the main stream, which was noticed by m e in Ann. & Mag. Nat. Hist. 1866, xviii. p. 30. Besides the species which will be mentioned subsequently, the following were collected by him at Xeberos:- Ageniosus brevifilis (C. & V.), Plecostomus emarginatus (C. & V.), Prochilodus nigricans (Agass.), Curimatus latior (Spix), Leporinus megalepis (Gthr.), Chalcinus brachypoma (C. & V.), Tetragono-pterus orbicularis (C. & V.), Myletes duriventris (Cuv.), Serra-salmo humeralis (C. & V.), Xiphorhamphus ferox (Gthr.), Sterno-pygus virescens (Val.). 2. A small collection from the Upper Amazons, made by Mr. Hauxwell, a correspondent of Mr. Bates, at Pebas. All the specimens contained in this collection have been previously described. 3. Two collections made by Hr. Kappler on the Maroni River, a river forming the boundary between the Dutch and French Guianas. 4. The freshwater fishes forming part of the museum of tbe late Dr. Van Lidth de Jeude. Unfortunately the localities whence these examples were procured are not preserved; but it is probable that the greater part, if not all, are from the Dutch possessions in Guiana, many of them being identical with species known to inhabit the fresh waters of Surinam. DORAS HELICOPHILUS. D. 1/6. A. 12. P. 1/8. V. 8. L. lat. 32-34. Lateral shields well developed, entirely uncovered by the skin ; the depth of the third is one-half of the length of the head, those on the tail only half as deep as the tail; their whole surface is covered with minute spines. The maxillary barbels reach to the middle of the pectoral spine, the outer of the mandible being somewhat and the inner much, shorter than those of the maxillary. Humeral process without spines, with a very slight ridge, extending to the hinder third of the pectoral spine. The posterior lobes of |