Where seen? This beautiful snail was seen on sandy areas
near lush seagrass meadows. Elsewhere, they are considered common
on sandy bottoms, especially on exposed sand flats and close to dead
coral areas. Intertidal and shallow subtidal zones to a depth of about
Features: 8-12cm long, elsewhere
about 9cm, up to 14cm. Shell typical helmet shape with a large body
whorl and tiny spire, thus resembling a bonnet. The shell is smooth
and grey without any markings. It has a notch in its shell so that
its siphon can be extended vertically upwards like a snorkel, probably
allowing it to breathe while it stays beneath the sand to hunt or
eat its prey. It has a white body and large yellowish foot which is
edged in brown, the operculum is fan-shaped and bright yellow.
What does it eat? According to
Tan, it feeds on sea urchins but according to Poutiers it feeds on
sand dollars. Some were seen on top of Cake
sand dollars (Arachnoides placenta) at Cyrene Reef. For
more gruesome feeding details, see Family Cassidae.
Baby bonnets: Egg capsules usually
form an irregular mass, the result of several females spawning together.
Human uses: It is collected for
food and for the shell trade.
Status and threats: The Grey bonnet
is listed as 'Endangered' in the Red List of threatened animals of
Singapore. It is threatened by habitat loss and over-collection. The
Book states that it has not been seen since the early 1970s and its
status needs investigation to determine if there are any remaining
On top of a Cake sand dollar.
Cyrene Reef, Aug 11
Notch in the shell for its siphon.
Juvenile with less developed shell.
Cyrene Reef, Aug 11
Photo shared by Loh Kok Sheng on flickr.
Buried with siphon sticking out.
Changi East, Oct 11
a sand dollar?
Cyrene Reef, May 11
shared by Marcus Ng on flickr.
Changi, Apr 09
bonnet snails on Singapore shores
Kusu Island, May 14
Photo shared by Marcus Ng on flickr.
- Tan Heok Hui
and Tan Siong Kiat. 30 November 2016. Grey bonnet preying on sand dollar at Changi. Singapore Biodiversity Records 2016: 166-167.
- Tan Siong
Kiat and Henrietta P. M. Woo, 2010 Preliminary
Checklist of The Molluscs of Singapore (pdf), Raffles
Museum of Biodiversity Research, National University of Singapore.
- Tan, K. S.
& L. M. Chou, 2000. A
Guide to the Common Seashells of Singapore. Singapore
Science Centre. 160 pp.
G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore
Red Data Book: Threatened plants and animals of Singapore.
Nature Society (Singapore). 285 pp.
- Abbott, R.
Tucker, 1991. Seashells
of South East Asia.
Graham Brash, Singapore. 145 pp.