Hypselostoma insularum Pilsbry, 1908

Figs 111 Y, 146, 147

Hypselostoma insularum Pilsbry, 1908: 41, fig. 2.

Hypselostoma insularum — Pilsbry 1917: 182–183, pl. 32, figs 1–4, 6; van Benthem Jutting 1950: 41.

Hypselostoma kentingensis Hwang, 2014: 30–32, fig. 2. syn. nov.

Type material examined.

Japan • lectotype of H. insularum; ANSP 95252 .

Type localities.

“ Yonakunijima, Ryuyku ”, Japan ( H. insularum); “ TAIWAN: Kenting Tropical Botanical Garden, Kenting, Hengchun, Pingdung, 21°58'04.5"N 120°48'55.3"E, alt. 295 m ” ( H. kentingensis).

Differential diagnosis.

This species is unique by its shell shape which resembles a pyramid (due to the sharp keel located at the base of the last whorl and moderately deep suture). All apertural barriers are strong but this is especially true for the angulo-parietal lamella.

Distribution.

This species is known from the type locality and Kenting Tropical Botanical Garden, Kenting, Hengchun, Pingdung, Taiwan (21°58'04.5"N, 120°48'55.3"E). The latter is the type locality of H. kentingensis .

Remarks.

Hypselostoma kentingensis is considered a junior synonym of this species since no major differences were observed between the two. All differences mentioned by Hwang (2014) in the original description are considered intraspecific variability. The statement in Hwang (2014) that H. kentingensis is smaller is not correct given the fact that the dimensions of the two species largely overlap (see Pilsbry 1917).