Wikipedia
Phenacolepadidae
Phenacolepadidae is a family of small sea snails or false limpets, marine gastropod mollusks in the clade Cycloneritimorpha (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).
This family has no subfamilies according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005.
Although the shell shape of genera in this family is that of a limpet, the family is in fact closely related to the Neritidae, the nerites.