Polymastia isidis var. simplex Hentschel, 1914

(Fig. 7A)

Polymastia isidis var. simplex Hentschel, 1914: 47, pl. V fig. 3; Plotkin et al. 2017: 1379.

The variety was described by Hentschel from Gauss Station, Antarctica, 66.0333°S 89.6333°E, depth 385 m (syntypes ZMB 4829). The differences of the syntype specimens with the typical variety described by Thiele (1905: 414, from Tierra del Fuego, Chile 54.3167°S 69.5°W, depth 19 m, holotype ZMB 3271) were declared by Burton (1932: 337–338) to be too minimal to keep the varieties as separate taxa. Plotkin et al. (2017: 1374–1378), however, discovered exotyles in the type of P. isidis, overlooked by Hentschel and also by Desqueyroux-Faúndez & Van Soest (1997: 421), who re-examined the type. Plotkin et al. transferred the type material of P. isidis to Sphaerotylus, but not the var. simplex as no exotyles were found in the syntype specimens of the variety (Plotkin et al. p. 1378, right hand column). Consequently, I propose here to formally elevate the var. simplex to a valid species to be named Polymastia simplex Hentschel, 1914 .