Rissoina artensis: Shell length up to 10.1 mm (N = 21); strongly elongate, subcylindrical. Protoconch : very small, of planktotrophic larval type, of 1 1/4, smooth, strongly oblique, whorls; sinusigera notch deep, with margin weakly thickened. Transition to teleoconch abrupt.
Teleoconch : of about 8 whorls; 4-5 adapical spire whorls strongly convex, strongly angulate below sutu¬res; subsequent spire whorls weakly convex to almost flat-sided; last whorl weakly convex, contracted near base. 4-5 adapical spire whorls with prominent, distantly spaced, very narrow, sharp and moderately opisthocline axial ribs with wider and deep interspaces; axial ribs gradually more densely spaced and less prominent on subsequent spire whorls; penultimate and last whorls with extremely short, densely spaced axial ribs, giving the sutures a strongly undulated appearance; last whorl with some, irregularly spaced axial folds, the latter
somewhat more numerous near varix. Spiral sculpture of threads, the latter more prominent
and more distantly spaced on adapical spire whorls, gradually less prominent and more closely spaced on subsequent spire whorls; penultimate and last whorls with numerous, very weak and very densely spaced,spiral threads; shell base with weak to mode¬rately prominent spiral cord.
Aperture : D-shaped, moderately large; inner lip thin, narrow, sometimes slightly thicker near shell base; anterior channel very shallow to almost absent; outer lip very thin, with very narrow, moderately thickened external varix; outer lip slightly opisthocline in profile. Colour : mostly rust-brown or white throughout. Operculum: typical of genus; peg open over all of its length. Radula : Inner and outer margin of lateral teeth with irregular and a rather irregular number of cusps.

As Moerchiella volvera:
Shell large, thin, cylindro-conical, elongate, white. Protoconch small, of 2,5 smooth whorls, sculpture beginning gradually on the 2nd whorl. Mature whorls 7, the first 4 short and turreted, the last 3 long and nearly equal in size. Sculpture of numerous axial ribs, well defined on the earlier whorls, where they number about 25 to the whorl, becoming weaker on the 3rd last whorl and only visible at the summit of the penultimate whorl. The body whorl is practically smooth, but there is a strong basal fold, and traces of the axial ribs can be seen in the deep, separating groove and on the edges of the fold itself. Aperture ovate, very obhque, sharply angled posteriorly, laterally and anteriorly well expanded, the outer margin thin with a wide but slight external varix, the columella with a shallow sinus. Length 10 mm.
Localities.—-Annan River (C. Hedley), holotype; Lindeman I.; Murray I. (Miss G. Thornley).
Remarks.—While the sculpture, texture, and aperture all conform to Moerchiella as defined, the strong basal fold at once separates it from all the other species, and indeed suggests that the difference is generic rather than specific. The discovery of further species may later justify this step.

Rissoina artensis: Apart from some variation in the strength of the basal spiral fold and in shell colour, the latter ranging from rust-brown to white, Rissoina (Moerchiella) artensis is rather uniform in shell characters.
The shell of Rissoina (Moerchiella) artensis very strongly resembles R. (M.) striolata, but differs in having strongly angulated spire whorls and in having sharp, distanly spaced axial ribs on the adapical spire whorls, rather than the closely spaced, rounded axial ribs in R. (M.) striolata; R. (M.) artensis has moderately prominent spiral threads on the adapical spire whorls, which are absent in R. (M.) striolata; furthermore, the protoconch of R. (M.) artensis is much smaller than the protoconch of R. (M.) striolata.
R. (M.) artensis is superficially similar in shell characters to R. (M.) dorbignyi, and is contrasted under that species.

Rissoina artensis: Tropical Indo-West Pacific. From Mozambique to Fiji. Australia. Queensland.

The type locality is New Caledonia. Hedley identified and labelled specimens which he collected at the Annan River, Qld., as this species. That figured is from a series collected by J. Laseron at Thursday I. It is 13 mm long. Others are still larger, up to 16 mm in length, but it is otherwise constant, except that some specimens show the curious distortion of the later whorls often found in the genus. It is also common at Murray I. (Miss G. Thornley), and islands in the Torres Strait.