Penniform Cone (Conus purus) size 7cm
The Penniform Cone is a Hawaii endemic species. They are found in shallow water. They mature where they hatch. This would make it hard to spread beyond Hawaiian waters. They are said to have a very strong venom. There are several similar cone shells. Kauai 2017
The Penniform Cone has a wide variation in appearance. This seems to be the most typical. Kauai 2017