Prosthiostomum multicelis Hyman 1953

Prosthiostomum multicelis Hyman, 1953 Prosthiostomum multicelis Hyman, 1953a: 384–386, figs 158–159 (type locality: San Gabriel Bay, Baja California Sur, Mexico). Prosthiostomum multicelis – Brusca 1980: 73, fig. 4.9 (new record from southern California and Gulf of California); 2005: 70 (new from record Espíritu Santo, San Gabriel Bay, Baja California Sur, Mexico). Distribution Pacific Northeast Temperate; Santa Catalina Island, California, United States; Puerto Refugio, Ángel de la Guarda Island, Baja California; San Gabriel Bay, Baja California Sur, Mexico. Habitat Benthic. Remarks Prosthiostomum multicelis is characterized by an elongated body with a rounded anterior edge and a blunt posterior region. Its dorsal surface is white or yellow, with a coloration pattern composed of orange speckles. The dorsal axis has a brownish line extending from the brain region to the third of the body, with yellow margins (Brusca 1980). Marginal eyes are distributed in the first third of the body, cerebral eyes are present and a conspicuous tubular pharynx. The male reproductive system is oriented towards the posterior region of the body, comprises oval accessory seminal vesicles, an elongate prostatic vesicle positioned posterior to seminal vesicles, and a penis papilla armed with a prominent stylet. The female reproductive system is oriented towards the anterior region of the body and features a tubular vagina.