Three colonial rhizocephalans from mantis shrimps and a crab in Vietnam, including Pottsia serenei, new species (Cirripedia : Rhizocephala : Thompsoniidae)

At Nha Trang, Vietnam, two species of colonial rhizocephalans of the family Thompsoniidae parasitize three species of Stomatopoda. Thylacoplethus squi llae Hoeg and Lutzen is already known from Japan. Pottsia serenei, new spec ies, may be differentiated from Pottsia plesionikae by its smaller size, re latively longer stalk, much larger eggs, and the presence of compound eyes in the cypris larvae. A third colonial species, Diplothylacus sinensis, is recorded from Portunus sanguinolentus at three localities in Vietnam.