Prosthiostomum sancum Du Bois-Reymond Marcus 1965

Prosthiostomum sancum Du Bois-Reymond Marcus, 1965 Prosthiostomum sancum Du Bois-Reymond Marcus, 1965: 131–134, figs 4–6 (type locality: Paita, Piura, Peru). Prosthiostomum sancum – Reyes et al. 2020: 3 (Paita, Piura, Peru, 5°4′50.1″ S, 81°6′13.4″ W, checklist). Distribution Northern Paita, Piura, Peru. Habitat Benthic, in the intertidal zone on rocky shore under a rock. Remarks Prosthiostomum sancum has a dorsal region with brown and black spots forming two dark bands, a cerebral region without pigmentation, and cerebral and marginal eyes present. The male reproductive system features a penis papilla armed with a curved stylet, and paired accessory seminal vesicles.