Plectostoma turriforme (van Benthem Jutting, 1952)
Benthem-Jutting (1952) original descriptions on Opisthostoma (Plectostoma) turriforme – “Shell high-turreted, light reddish-brown. Top whorls often darker because of the retracted animal, or of remaining fragments of disintegrated tissue shining through. Protoconch of 1 ½ whorl smooth. Subsequent whorls ornamented with fine oblique white ribs, distantly placed and standing out wing-like away from the shell, especially on the periphery, rendering the profile of the shell falsely angular. No spiral sculpture visible. Not transparent or shining. Whorls 9-10, convex, regularly increasing in size. Top whorls not markedly oblique on the rest of the shell. Last whorl about midway somewhat constricted transversely, then widening again and irregularly coiled, although not so bizarre as in any of the previously mentioned species of this subgenus. Suture deep. Umbilicus as a narrow slit, or closed by the last whorl hiding the opening. Aperture trumpet-shaped, round, adnate. Position almost vertical, but in occasional specimens slightly oblique, either directed downward or upward. Peristome continuous, almost circular, duplex. Operculum unknown.”
“…on renewed investigation, spiral striae proved to be present.” (Benthem-Jutting, 1961)