Trochus

Trochus is a genus of medium-to large-sized, top-shaped sea snails with an operculum, of the family Trochidae, the top snails.

When the word "trochus" or "Trochus" is used in reference to fishing sea snails for commercial purposes, the usual species targeted is Tectus niloticus, which is valued for its nacre or mother of pearl layer, which was traditionally made into items such as pearl buttons and jewelry. Tectus niloticus is no longer classified as a Trochus species, and it is no longer classified in the family Trochidae; it is now placed in the family Tegulidae.