Order: Sorbeoconcha (Neotaenioglossa)
Superfamily: MURICOIDEA


Cystiscus sp. Fly Point, Port Stephens, New South Wales, Australia. March 1987. AM C152942. Photos: Bill Rudman.

The marginellids are a group of small marine snails whose shell has a characteristic smooth polished surface. We don't know much about their biology and their diet seems to vary from species to species. Some, such as the species of Cystiscus illustrated here, feed on bryozoans, but others are reported to feed on ascidians, burrow through bivalve shells, and to attack sleeping fish. They often have brightly coloured animals and partially enclosed shells which may make them look like a small bubble-shell. They are however not related to opisthobranchs.

Authorship details
Rudman, W.B., 2002 (March 18) Marginellidae [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

Is Gibberulina an opisthobranch?

March 20, 2002
From: Nishina Masayoshi

Dear Bill,
This animal is called Gibberulina tantilla in a some Japanese Shell and Nudhubranchs ID book. If it's correct, is it a snail or an opisthobranch? Its head looks quite like the head shape of Colpodaspis to me.

Date: 15 April, 2001
Location: Hachijo Island Japan
Depth: 7m
Length: 3mm

Best Regards,
Nishina Masayoshi

Masayoshi, N., 2002 (Mar 20) Is Gibberulina an opisthobranch?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Nishina,
This animal is a snail of the family Marginellidae. Its head does have the look of Colpodaspis and unlike most snails, the eyes do not seem to be associated with tentacles. But its shell and anatomy are definitely not opisthobranch.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Mar 20). Comment on Is Gibberulina an opisthobranch? by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from