Caligusselenecola sp. nov. (Siphonostomatoida, Caligidae) parasitic on the hairfin lookdown Selenebrevoortii (Gill) from the Gulf of California, Mexico, with some comments on Caritustolii Rangnekar, 1984.

Specimens of a caligid copepod (Siphonostomatoida) were found on the gills of the hairfin lookdown Selenebrevoortii (Gill) (Carangidae) from off Mazatlán, Sinaloa (north-western Mexico). This material represents a new species of Caligus , C.selenecola sp. nov. , and is assigned to the diaphanus species group. Within this group, only C.kapuhili Lewis, 1967, C.laticaudus Shiino, 1960, C.macrurus Heller, 1865, and C.selenecola sp. nov. , have been described with a reduced outer spine 1 on the second exopodal segment of leg 1. These four species can be readily separated by the relative length of the abdomen, and the presence/absence of a process on the myxal area of the female maxilliped, the sternal furca, the postantennal process, and the spiniform process on the basal antennary segment. A full description of the new species is given with some comments on Caritustolii Rangnekar, 1984.