Plectostoma panhai (Maassen, 2001)

Maassen (2001) original descriptions on Arinia panhai – “Shell dextral, conical, light brown, shining and transparent; with six moderately convex whorls, separated by a deep suture, and with a distinct spiral striation. The penultimate whorl slightly wider than the body-whorl. Radial ribs rather thin, increasingly higher and sharper on the lower whorls; on the penultimate whorl 6-8 ribs/mm, above the aperture 7-8 ribs/mm. The constriction consists of a transversal thickening all around, and of a small but distinct, longitudinal tubercle at the angular edge, just entering the transversal thickening. The tuba is 0.7 whorl long. Umbilicus widely open, eccentric, showing part of the penultimate whorl. Peristome doubled, the inner peristome only slightly protruding from the outer. The aperture is situated to the right of the middle of the previous whorl and clearly turned upwards. Operculum corneous, with a distinct spiral ridge on its outer surface.”