Distribution and prevalence records of two parasitic barnacles (Crustacea : Cirripedia : Rhizocephala) from the west coast of North America

New records of rhizocephalan barnacles from the Mexican Pacific are present ed. The distribution ranges of Lernaeodiscus porcellanae (Lernaeodiscidae) and Heterosaccus californicus (Sacculinidae) and their host species are rev ised. In both cases, the parasites occur in only a fraction of the total ge ographic range of their hosts. Lernaeodiscus porcellanae was found only in the porcellanid crab Petrolisthes cabrilloi from Laguna Beach, California t o San Quintin, Baja California; while H. californicus ranged from Bodega Ba y, California to Cedros Island Baja California parasitizing (fi om north to south) the majid crabs Pugettia producta, Loxorhynchus grandis, L. crispat us, and Taliepus nuttallii. Prevalence records are presented for Lernaeodis cus porellanae and for H. californicus parasitizing I? producta; in both ca ses considerable geographical and temporal variation was found.