Giant Top (Rochia nilotica) サラサバテイ – size < 10cm – Commercial top shell
The Giant Top can get over 10 cm in diameter. They are eaten and the shell is used for mother of pearl. The shells are usually covered with encrustations. Before 2018 this shell was known as Tectus niloticus. Amami 2019
This is the bottom of the same Giant Top with the animal partially visible. Amami 2019