Assiminea aldra
Assiminea aldra is an extinct species of small operculate snail, a marine gastropod mollusc or micromollusc in the family Assimineidae.
Description
The length of the shell attains 2 mm, its diameter 1 mm.The shell is minute, composed of about five moderately rounded whorls with a distinct suture. The spire tapers evenly to a somewhat blunt apex, and the surface is smooth.
The body whorl comprises more than half the length of the entire shell.
The aperture is rounded ovate, and the peristome is moderately thickened but not reflected. There is a well-marked layer of callus on the body whorl, and the umbilical region is imperforate.