Folda (1928) described Megalocotyle marginata from Sebastodes nebulosus, taken in Puget Sound, Washington, as a new genus and species. Both Price (1939) and Sproston (1946) not only accepted the genus as valid, but extended it to include two European species unlike the proposed species. Eight individuals of the proposed species were taken from the gills of Sebastodes paucispinus (Ayres) collected offshore from Newport, Lincoln County, Oregon, February 24, 1951. Seven specimens were prepared as whole mounts, while the eighth one was serially sectioned. Subsequently 6 more specimens were taken from the same host and locality on July 21, 1952.