Alvania densecostata

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

Description
The length of the shell attains 3 mm, its diameter 1 mm.

(Original description) The solid, minute shell is elongate-turreted. The whorls are convex. They are ornamented by numerous fine, nearly straight ribs, crowded closely together, intersected by spiral striae which become stronger and more prominent below the periphery.

Distribution
Fossils of this species were found in late Pliocene strata at St. Erth, Cornwall, Great Britain.