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.