Taxon classification Animalia Mesogastropoda Diplommatinidae

Diancta macrostoma (Mousson, 1870) Figs 2-4

Diplommatina martensi var. macrostoma Mousson 1870, Journal de Conchyliologie, 18: 184, pl. VIII, fig. 5. Type locality: "Ovalau, Vaini Loba et quelques autres points de Viti Levu".

Diancta macrostoma Möllendorff 1897, Nachrichtsblatt der deutschen malakozoologischen Gesellschaft, 29 (1/2): 44.

Type data.

Diplommatina martensi var. macrostoma Mousson: lectotype, here designated, ZMZ 526691a, paralectotypes ZMZ 526691/5, Ovalau, coll. Mousson ex Graeffe 1866. - macrostoma Möllendorff: lectotype designated by Zilch (1953: 18) SMF 104905/1, Fiji ["in insula Vitilevu"], coll. Möllendorff ex Mousson.

When establishing Diancta macrostoma as a new species, Möllendorff cited " Diplommatina macrostoma Mouss. ms.", apparently unaware that Mousson had already described it as Diplommatina martensi var. macrostoma . The two names are homonyms but, as they are not based on the same name-bearing types, they are not objective synonyms.

Diagnosis.

Shell sinistral, elongate, sculpture of widely spaced ribs, ribbing pattern constant throughout teleoconch.

Description.

Shell sinistral, elongate oval, yellowish; last whorl constricted; protoconch broad, obtuse, with a fine pattern of granules; umbilicus closed, concave narrow periomphalum; teleoconch sculpture of coarse widely spaced ribs, ribbing pattern constant throughout the shell, somewhat denser on the dorsal side of penultimate whorl; aperture broadly subquadrate, peristome doubled, with the upper left edge slightly protruding; apertural rims connected by a thin, slightly detaching callus; aperture only just attached to the last whorl; no pleats visible in the aperture; inside the shell, two small columellar plates present.

Operculum corneous, flat, internally with a small lamella.

Measurements.

Lectotype (Fig. 2): H = 2.86; D = 1.93; PH = 1.4; PD = 1.35; W = 5.

Distribution

(not shown on map). Ovalau Island.

Remarks.

Mousson also recorded this species from Viti Levu. The re-investigation of his specimens revealed that none of them is conspecific with the lectotype of Diancta macrostoma . For revised identification of these specimens, see Tab. 2.