The polyclads (Platyhelminthes: Polycladida) from the Tropical Eastern Pacific: Commented checklist and description of a new species Author Ramos-Sánchez, Mariela E9D05B3F-CF64-48E3-B5ED-8D24E47F9D2A Doctorado en Ciencias Biológico Agropecuarias, Área Ciencias Biológico Agropecuaria y Pesquera, Ciudad de la cultura “ Amado Nervo ”, Tepic, Nayarit, 63000, Mexico. & Laboratorio de Sistemática de Invertebrados Marinos (LABSIM), Universidad del Mar, campus Puerto Ángel, Ciudad Universitaria, Puerto Ángel, Oaxaca, 70902, Mexico. rmariela220@gmail.com text European Journal of Taxonomy 2024 2024-10-17 962 1 1 67 https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2683/12419 journal article 10.5852/ejt.2024.962.2683 2118-9773 13947260 40171C5B-90EB-4641-91FF-EA8CA2C60D23 Spinicirrus inequalis Hyman, 1953 Spinicirrus inequalis Hyman, 1953a: 347 , 350–353, figs 114–117 ( type locality: Pardita Island, La Paz Bay, Baja California Sur , Mexico ). Spinicirrus inequalis – Brusca 2005: 69 (checklist). Distribution Pardita Island, La Paz Bay, Baja California Sur , Mexico . Habitat Benthic. Remarks Spinicirrus inequalis is characterized by an elongated body with a rounded anterior end, cerebral eyes arranged in two groups and distributed in a rounded shape and tentacular eyes distributed in two continuous bands; without nuchal tentacles. The male reproductive system lacks bulbs and spermiducal vesicles, presents a cirrus sac armed with teeth; in sagittal view, a glandular pouch is observed positioned in the anterior region of the spermiducal vesicles, with teeth distributed in two groups: a pair in the region posterior to the glandular pouch and approximately two pairs in the region anterior to the male atrium ( Hyman 1953a: 352 , fig. 117); in ventral view, these spines are distributed in two groups: one formed by a pair of teeth and the second group presents a total of 15 teeth ( Hyman 1953a: 352 , fig. 116). The species also has an oval digitiform prostatic vesicle. The female reproductive system presents a dorsally positioned vagina without Lang’s vesicle. Hyman (1953a) schematized an elongated sac anterior to the vagina, however, the functionality of this structure is unknown. Hyman (1953a) suggested collecting more specimens to better define the specific composition of the reproductive system of the species, as well as its systematic position within the family Planoceridae .