Ethminolia Iredale, 1924

Herbert, David G., 2024, The Umboniinae (Mollusca: Gastropoda: Trochidae) of New Caledonia, with descriptions of two new genera and eight new species, plus an additional new species from the Bismarck Sea, European Journal of Taxonomy 973, pp. 1-143 : 98-100

Genus Ethminolia Iredale, 1924

Ethminolia Iredale, 1924: 228 .

Type species

Ethminolia probabilis Iredale, 1924 (original designation), Recent, SE Australia. Generic fossil record: Quaternary to Recent ( Paleobiology Database 2024) ( Fig. 52 ).

Diagnosis

Shell small (diameter usually <10 mm), width considerably greater than height; whorls rounded, often shouldered; sculpture of spiral lirae or cords with microscopic axial threads; umbilicus broad, its rim rounded and not thickened, lacking an internal funicle; outer lip simple, interior nacreous, without in-running ridges.

Operculum corneous, multispiral with well-developed, radially striate peripheral fringe, striations remaining evident on earlier whorls; spiral microsculpture present.

Radula with base-plates of rachidian and lateral teeth thin, narrowing anteriorly, outer edge rounded, raised anteriorly and somewhat twisted; fifth lateral scarcely evident; inner marginal tooth transitional with reduced cusp; cusps of inner marginals short and broad, 2–10 largest, coarsely dentate, central denticle asymmetrical and somewhat broader; additional narrower denticles on both margins.

Ctenidium unknown.

Remarks

This diagnosis of Ethminolia is tentative as the type species remains poorly known. In an attempt to remedy this, I have examined the radula and operculum of topotypic material from the Melvill-Tomlin collection (NMW) and here provide illustrations thereof for the first time ( Fig. 52 ). The cusp morphology of the inner marginal teeth differs significantly from that of Ethalia , Sericominolia and Talopena and other genera belonging to Group 1. Many of the species currently referred to Ethminolia will doubtless prove referable to other genera when studied in more detail. I refer the following new species to Ethminolia with some hesitation since although the shell is somewhat similar to that of E. probabilis , as are the cusps of the inner marginal teeth, I could not discern either spiral microsculpture on the operculum, nor an intermediary inner marginal tooth.

Figures

Fig. 52. Ethminolia probabilis Iredale, 1924, operculum and radula, Twofold Bay, New South Wales (NMW 1955.158). A. Entire operculum. B. Microsculpture of operculum. C–G. Radula. Scale bars: A=0.5 mm; B=100 µm; C, E= 25 µm; D, F–G=20 µm.