Rissoina antoni: Described in French (click French flag)

Shell length up to 12.5 mm (N = 27); solid, narrowly to elongately conical. Protoconch of non-planktotrophic larval type, of 1 1/4 whorls; last whorl with 2-3, distantly spaced, spiral threads (only present in fresh specimens). Transition to teleoconch abrupt; sinus very shallow. Teleoconch : of about 9 whorls; adapical 4-5 spire whorls strongly angulated below sutures, subsequent spire whorls becoming gradually less angulate; last whorl weakly inflated. Axial sculpture of adapical spire whorls consisting of prominent, rounded, almost orthocline, axial ribs, gradually more prominent, wider and more distantly spaced on 3rd to 6th spire whorl, usually becoming gradually less prominent on subsequent spire whorls, eventually absent on last whorl; absent on last two whorls in some specimens; some with weak, very short axial ribs on adapical 1/3 of last whorl. Spiral sculpture of moderate to very prominent spiral cords on adapical spire whorls, numbering 4-5 on first and second whorls and usually 3-4 on third to sixth whorl; spiral cords intersecting axial ribs, forming prominent, rounded nodules on latter; spiral cords usually becoming gradually less prominent, more irregular and more irregularly spaced on abapical spire whorls and on last whorl (usually with some very irregular and irregularly spaced spiral threads on last whorl, but some specimens with rather prominent spiral ribs on last whorl).
Microsculpture of crowded, flat-topped, spiral threads, with narrower interspaces. Aperture : D-shaped to lenticular, rather small; inner lip very thin; columellar side moderately concave; anterior channel short, shallow; outer lip, with thick, rounded, wide, external varix; outer lip strongly opisthocline in profile. Colour: white throughout.

Rissoina antoni: Rissoina (Moerchiella) antoni shows considerable variation with respect to both the shell shape and shell sculpture; the spire ranges from strongly to weakly elongated; furthermore, the last whorl is usually moderately inflated, but in some specimens it is only weakly convex. In all specimens available from Mozambique, Madagascar, Reunion and the Maldives, the adapical spire whorls are weakly angulated, while the adapical spire whorls are strongly angulated in all specimens available from Java, Australia and New Caledonia (cf. Remarks). The strength of the spiral sculpture on the adapical spire whorl ranges from moderately prominent in specimens from the Indian Ocean, to very strong in specimens from Java, Australia and New Caledonia. The strength of the spiral sculpture on the penultimate and last whorl is strongly variable, ranging from very weak, crowded, spiral threads to prominent, more or less distantly spaced, spiral ribs.
The shell of Rissoina (Moerchiella) antoni strongly resembles R. (M.) dorbignyi, but is distinguished by its markedly shorter aperture and by the less canaliculated sutures of the adapical spire whorls.

Rissoina efficata: Shell elongate, solid, white, smooth ; whorls 7, flattened, the three upper having two spiral granulated ridges on the centre of the whorls ; suture deep, aperture semiovate ; inner lip moderately callous, outer lip very much thickened, white, slightly sinuated anteriorly.
Length, 4 lines; breadth, 1,5 line.
Hab. Barnard Islands, No. 3, North-east Australia ; found under blocks of coral.

Rissoina antoni Schwartz, 1860
Rissoina (Moerchiella) antoni Schwartz, 1860 in Kuroda (1941)
Diagnosis: Shell, elongate oval-conic with apex, blunt. Mature whorls 5, slightly convex and suture channelled. Reticulate sculpture replaced by spiral cords on the lower half of body whorl; 4 spirals and about 16 axials on the penultimate whorl. Aperture, semicircular with columella, slightly concave and outer lip, thicken by smooth varix. It looks like Phosinella villica (Gould) but this shell is stouter with less mature whorls and its aperture is broader.
Distribution: Java, Indonesia is the fatherland. It was recorded in Taiwan by Kuroda, 1941.
Dimension: 5.3 x 2.0 mm.
Reference for Identification: Schwartz (1860), sp. 63; Weinkauff (1885), Taf. 5-8, 9, 10; Kuroda (1941), sp. 181.

Rissoina antoni: Possibly R. (M.) antoni SCHWARTZ is a species complex, consisting of two or more species; the morphotype from the East African Coast, Madagascar, Reunion and Maldives differs from the morphotype from Australia and New Caledonia in having less prominent spiral ribs on the adapical spire whorls and in having less angulated adapical spire whorls. Nevertheless, additional data with respect to the anatomical characters (penial characters and possible differences in relative strength of the sperm duct in the female), are needed to judge whether the morphotypes are separate species or if the differences in sculpture are the consequence of a trans-Indo-West Pacific cline. In the original description of the nominal variety pusilla of R. antoni, NEVILL (1884) only referred to the small size of the specimen without reporting any further differences with the reference species. The shell dimensions of the specimen, housed in the collections of the ZSI (reg. No. M. 10955/2), labeled "Rissoina antoni var. pusilla NEV., loc. 7" agree with the dimensions given in the original description, so that it can be concluded with a relatively high certainty that it represents the holotype of this nominal variety.

Rissoina antoni: Indo-West Pacific, from Mozambique to New Caledonia