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.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.