Metynnis longipinnis sp. n. – a new species of Silverdollar from the río Casiquiare drainage in Venezuela is described. The new species is closely related to Metynnis hypsauchen (MÜLLER & TROSCHEL, 1844) according to its features (1) high number of gill-rakers, (2) long adipose fin, (3) deep body, (4) short head and (5) long occipitale and is clearly defined because of (1) the high number of serrae (36–37 vs. 27–32 of M. hypsauchen), (2) the small scales (91–93 vs. about 75–83), (3) uniformly silver colouration and (4) the extremely elongated dorsal fin and anal fin. From Metynnis altidorsalis AHL, 1924 the new species is clearly differentiated by its (1) number of gill-rakers (30–33 vs. 20–25 for M. altidorsalis), (2) the number of branched anal rays (37–40 vs. 32–37 for M. altidorsalis), (3) the number of serrae (36–37 vs. 29–35 for M. altidorsalis) and (4) the length of the occipitale (18.94–20.78 % SL vs. 11.7–15.6 for M. altidorsalis). Further on M. longipinnis sp. n. has a longer adipose fin (20.00–20.78 % SL vs. 11.8–16.2 for M. altidorsalis) and an elongation of the rays of dorsal and anal fin (vs. not elongated for M. altidorsalis). M. luna COPE, 1878, M. orinocensis (STEINDACHNER, 1908) and M. guaporensis EIGENMANN, 1915 are differentiated by its higher number of gill-rakers and lager head length. M. lippincottianus (COPE, 1870) has a completely different colouration. Metynnis polystictus sp. n. – a new species of Silverdollar from the río Xingu in Brazil is described. The new species is closely related to Metynnis anisurus AHL, 1924, which is considered as valid. M. polystictus sp. n. is clearly differentiated from M. anisurus by its (1) colouration (body without spots in M. anisurus vs. two different kinds of spots in M. polystictus sp. n.) and (2) the enlarged lower lobe of caudal fin (developed in M. anisurus vs. absent in M. polystictus sp. n.). The Synonymy of Metynnis goeldii EIGENMANN, 1903 with Metynnis lippincottinianus (COPE, 1870) could be confi rmed, because of the rediscovery of a syntype of Metynnis goeldii EIGENMANN, 1903 in the collection of the California Academy of Sciences (San Francisco).
A new species – Hemigrammus geisleri sp. n. – from the central Amazon in Brazil (Amazonas) is described (Teleostei: Characiformes: Characidae). It is a small species of the genus Hemigrammus Gill, 1858 (lateral line incomplete, basis of caudal fin scaled, fi ve teeth in the second row of premaxillary bone), which differs from all congeners through the following combination of features: (1) two to four tri- to quincuspid teeth in the external row of premaxilla, (2) fi ve (rarely six) quincuspid teeth in the internal row of premaxilla, (3) one to two (rarely three) maxillary teeth, (4) 16–18 (mostly 17) branched anal fin rays, (5) 29–31, mean 30, longitudinal scales, (6) 8 to 14 pored scales in lateral line, (7) 4/1/3–3½ transversal scales before dorsal, (8) 32 to 33 vertebrae and (9) a oval spot at the basis of caudal fin.
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