Triathrix montagni and T-kalki, a new genus and two new species of Cletodidae (Crustacea: Copepoda: Harpacticoida) from California and the Gulf of Mexico

Triathrix new genus (Copepoda, Harpacticoida, Cletodidae) is established to accommodate T. montagni new species from the California continental shelf and T. kalki new species from the Gulf of Mexico. The genus is characterised by a triangular, sharply pointed rostrum; a chitinous extension bearing four socles on the posterior border of the cephalothorax; no socles on the preanal somite; a median tube pore on the operculum; seta I of the caudal ramus implanted posterior to sera II; antennal exopod with three setae; mandibular palp with five setae; maxillulary coral endite with one seta and basal complex with eight setae; maxillary proximal syncoxal endite with two elements, allobasal endite with a spine and two setae, endopodal setae not fused at base; maxillipedal syncoxa without seta; no sexual dimorphism on male P3; female P5 with baseoendopodal lobe and exopod long, rectangular and equal in length. The two species can be distinguished easily from each other by the size of the dorsal extension to the cephalothorax, the shape of the dorsal median socles on the free prosomites, the length of setae on the P1 and male P5 baseoendopodal lobe and the length to width ratio of the caudal rami and the female P5. Enhydrosoma nicobarica Sewell, 1940 is also included in the genus as T. nicobarica new combination.