Phascolosoma (Phascolosoma) agassizii agassizii Keferstein, 1866: 218–219,

as Phascolosoma agassizii; type locality: Mendocino, California. — Steinbeck & Ricketts 1941: 345–346 (under boulders, intertidal, Point Lobos, Espíritu Santo Island, Baja California Sur). — Brusca & Thompson 1977: 44, as P. agassizii (Cabo Pulmo reef, Baja California Sur, Mexico, in coral). — Brusca 1980: 126, as P. agassizii (Gulf of California, Mexico). — Dean et al. 2010: 62, as P. agassizii (Point Ulloa, Costa Rica, in calcareous rock).