· Alvania cosmia is a species of small sea snail, a marine gastropod mollusk or micromollusk in the family Rissoidae.

It is marked by two strong nodulose, spiral keels, of which the first is situated on the angle of the shoulder, while the second is about as far posterior to the suture as the first is anterior to the summit.

The spaces enclosed between the spiral keels and axial ribs are large, deeply impressed, squarish pits, while their junctions form cusp-like tubercles.

The base of the shell is moderately long, marked by three spiral keels, which grow successively weaker and closer spaced from the periphery to the umbilical area.

The outer lip is reinforced immediately behind the edge by a strong varix, transparent, showing the external sculpture within.