Pericelis ernesti Hyman 1953

Pericelis ernesti Hyman, 1953 Marcusia ernesti Hyman, 1953a: 296–298, figs 32–33 (type locality: Gulf of California, Mexico). Pericelis ernesti – Hyman 1955d: 263 (new combination). — Soutullo et al. 2021: 373, fig. 6b–e (new record from Playa Carbón Beach, in Las Baulas National Marine Park of Guanacaste, Costa Rica, 10°20′53.4″ N, 85°51′44.5″ W). — Tsuyuki et al. 2021: 1–15 (mention only). Marcusia ernesti – Lamothe-Argumedo et al. 1997: 15 (new record from Guaymas, Sonora, Mexico). Distribution Punta Marcial, Cabo Pulmo National Park, Baja California Sur; Puerto Peñasco, Sonora; Clarión Island, Revillagigedo Island, Manzanillo, Colima, México; Playa Carbón Beach, in Las Baulas National Marine Park of Guanacaste, Costa Rica. Habitat Benthic. Remarks Pericelis ernesti was initially established by Hyman (1953a) within the suborder Acotylea (family Cryptocelidae) as Marcusia ernesti. Hyman (1953a) described it as a very peculiar acotyleo that presents characteristics of the suborder Cotylea, such as the distribution of the marginal eyes and the presence of a cement bag in the cement glands, which are emptied by a pair of ducts (see Hyman 1953a: 287), structures that sensu Hyman (1953a) are characteristic of the genera Pericelis and Enchiridium Bock, 1913 (suborder Cotylea). Hyman (1955d: 263) later transferred the species to the genus Pericelis (family Pericelidae, suborder Cotylea) based on the arrangement of the eyes, the coloration pattern (reticulate), the presence of a ventral sucker, and the reexamination of the male and female reproductive system. Faubel (1984b) subsequently reestablished the species as M. ernesti and transferred it to the family Anonymidae Lang, 1884, but did not mention the criteria for the reestablishment of the species, only mentioning that Hyman (1953a) overlooked the presence of a sucker. Prudhoe (1985) established Marcusia Hyman, 1953 as a junior synonym of the genus Pericelis, but did not substantiate the criteria for this decision. On the other hand, Cuadrado et al. (2021), through a molecular analysis based on the 28S marker, validated the separation of Marcusia (represented by Marcusia alba) from the genus Pericelis. This finding contrasts with Tsuyuki et al. (2021) who determined Marcusia as a junior synonym of Pericelis based on a molecular analysis based on the concatenation of the 18S and 28S genes. Therefore, the present study suggests a comprehensive review of the biological material of the 12 species of Pericelis.