Just came across this on ChimCK's flickr!
This is what ChimCK shared about the snail.
Variegated Sundial (Heliacus variegatus)
A possible first record in Singapore.
This specimen was laying an egg mass in the aquarium three weeks after being collected from Cyrene Reef.
The operculum of this marine snail is conical, which is uncommon in gastropods. I wonder if the shape of the operculum is an adaptation for the diet of this zoanthid-feeding animal.
Isn't Cyrene just amazing! And thanks as well, to the many scientists studying this reef.