Ompok argestes, a new species of silurid catfish endemic to Sri Lanka (Teleostei: Siluridae).

Ompok argestes, a new species of silurid catfish, is described from the southwestern lowlands of Sri Lanka. The new species is distinguished from all other species of Ompok in the Indian subcontinent by a combination of the following characters: body color pattern mottled; predorsal profile uniformly convex; maxillary barbels reach or extend slightly beyond base of dorsal fin; eye diameter 14.2-17.1% head length (HL); body depth at anus 19.8-22.3% standard length (SL); head width 14.3-16.8% SL; caudal peduncle depth 5.6-6.5% SL. Callichrous ceylonensis Günther is shown to be a valid species that is apparently restricted to Sri Lanka, distinguished by a combination of the following characters: distinct concavity in predorsal profile; origin of pelvic fin beneath or slightly posterior to the origin of the dorsal fin; maxillary barbels 108-166 % HL; mandibular barbels 16.1-33.7 % HL; and 58-66 anal-fin rays.