Nipponacmea

Nipponacmea is a genus of sea snails, the true limpets, marine gastropod mollusks in the family Lottiidae.

The color of the shell is greenish brown and characteristically bedecked with granules of fine radial riblets.

The thin and broad interior shell margin exhibits a distinct color and texture from the adjoining area.

[1] They were reassigned based on different anatomical characters and shell structure and their endemism to the Japonic zoogeographical province (Japanese waters and adjacent island chains).

Some authors consider them color variations, others regard them as subspecies or as independent species.