Alvania minuta

Alvania minuta is an extinct species of minute sea snail, a marine gastropod mollusc or micromollusk in the family Rissoidae.

Taxonomy
Alvania minuta (Golikov & Fedjakov, 1987) is a homonym and has become a synonym of Pusillina tumidula (G. O. Sars, 1878).

Description
The length of the shell attains 1.5 mm, its diameter 0.9 mm.

(Original description) The minute shell is oval, clathrate and imperforate.

The protoconch consists of 2 globose glossy whorls. The nucleus is minute, rapidly enlarging.

The teleoconch contains about 2 whorls, indistinctly shouldered just below the suture, then flatly convex. The body whorl is bluntly angled, its base almost flat.

The axial sculpture commences first, consisting of strong bluntly-rounded ribs, sloping forwards and reaching from suture to suture, the interstices narrower; they number about 19, and cease just below line of suture on the body whorl. The axials are crossed by much weaker spirals, indistinct on early whorls, 4 on penultimate whorl, broad and flatly rounded (interstices sublinear) and cutting up axials into blunt laterally-elongate tubercles. A fifth spiral emerges from the suture-line on to base and is slightly crenulated by ends of axials. Below this are 2 smooth and much fainter ribs, the rest of base smooth.

The spire is a little higher than the aperture. The suture is much impressed. The aperture is slightly oblique, sub-ovate, angled above, effuse below. The peristome is discontinuous. The outer lip is thin, but does not appear to be finished. The arcuate columella is slightly oblique.

Distribution
Fossils of this marine species were found in Tertiary strata in New Zealand