Sundial shells are fairly unique in being a noticeably disc-shaped shell, flattened and in showing a lenticular edgewise appearance. Shell belongs to genera, Architectonica and is believed to be associated with the Sun God and "The Sun" of the Tarot Card. Ever-widening whorls of phylum Mollusc extensively distributed in warmer waters of the West and East coasts of North as well as of South America, and Indo-Pacific regions. Sundial Shells are of box-like or dome-shaped structure and hornier rather than calcareous.
The shell 8 cm in diameter has beautiful spirals in white, ashy, black and shades of brown. The body and fat tentacles are striped to match the shell of this snail. The mouth region of this shell is lined with a tough cuticle as a guard against the stings of their prey; they eat burrowing sea anemones and sea pens. In the Red List of threatened animals of Singapore, the Clear sundial snail is listed as 'Endangered’ and the original shores where they were found have been lost to reclamation.
This shell is a treasure in any collection, but as its name it does not tell time. With either gobbet (bubbled like) or a smooth surface, the bottom of the shell is curved in (concave) and bears a resemblance to a staircase. In the shell world, the design of this shell is said to be most intricate.
The shell gets its name from its circular appearance which resembles the Sun, but it too has different names like a perspective sundial, oriental sundial and painted sundial in different parts of the world. The average size of this shell ranges between 2.5 – 5 cm and belongs to class Gastropoda.
The upper side of the shell is lighter in colour ranging from white to yellowish – brown dorsal shell, whereas brown dots can be seen in the periphery and underneath the inner circle of the shell. Sundial shells dwell in shallow sandy areas, so are rarely found on the shore. The round shape of the shell allows the snail to lair in the sand around 1.5-120 meters deep.
These beautiful shells are collected by shell dealers and are easily available in curio shops. The head of the snail in the shell contains a pair of long, slender tentacles that abet chemoreception eyes at their outer bases. Two pointed lobes can be seen at the end of the slimy foot sundial snail. Being a hermaphrodite animal, they lay eggs in egg capsules embedded in a gelatinous mass. The larva of the sundial is called veliger, these larvae become an important food source for fish and other larger organisms. Truly, the clear sundial shells when polished become glossy and shines brightly like a sun catching the eye of bystanders!