The families Marginellidae and Cystiscidae (formerly lumped under Marginellidae) are small prosobranch snails (usually less than 5 mm) that often have transparent shells. In many cases, the mantle is brightly colored and shows through the shell allowing them to be mistaken for cephalaspideans. They can be distinguished from the latter by the bulbous eyes at the bases of their cephalic tentacles. Several other families of prosobranchs also have small members in which the mantle colors show through the shell. Representative Hawaiian species:

Crithe sp. #1 CP: Maliko Bay, Maui April 19, 2008

Cystiscus sandwicensis CP: Hekili Point, Maui Oct. 5, 2002

un. cysticid sp. #1 CP: Airport Beach, Maui April 12, 2012

For more information see: The prosobranch addendum on this site for Marginellidae and Cysticidae Kwajalein marginellids & cysticids by Scott & Jeanette Johnson