Rhytidocystis is a genus of apicomplexans.[1] It is the only genus within the monotypic family Rhytidocystidae.[2] The species of this genus are parasitic protozoa found in marine annelids.
^Levine, ND (1979). "Agamococcidiorida ord. n. and Rhytidocystidae fam. n. for the coccidian genus Rhytidocystis Henneguy, 1907". J Protozool. 26 (2): 167–8. doi:10.1111/j.1550-7408.1979.tb02756.x.