CASSIDAE

'Helmet shells', as it is more popularly known, are distinguishable from other gastropods by the following characteristics:

External

1. short spire large enveloping body whorl often having ribs, knobs or varices.

2. thickened outer lip, often toothed.

3. anterior siphonal canal short and frequently twisted.

4. most have bright bands and spotted colour patterns on shell.

Internal

1. very large accessory salivary glands (compared to other tonnoideans).

2. significantly longer marginal tooth, usually serrated at tips.

3. salivary ducts passing through nerve ring (similar to Ranellidae)

Habitat: often subtidally or intertidally, commonly on sand or rocky substrates.

Feeding:

Scientific literature, though not many, had highlighted on the feeding ecology of some members of the Cassidae (Hughes & Hughes 1971, 1981; Hughes 1986). Generally, members of the Cassidae are echinoid (sea urchin) feeders, in addition to some others preying on bivalves and asteroids (seastars). The phaliine (one of the subfamilies of Cassidae), Phalium bisulcatum, reportedly found in our local shores, had broken spines of an echinoid found in gut samples (Taylor 1982). It also preys on Brissus latecarinatus (Echinodermata: Echinoidea) under experimental conditions (Hughes 1983).

The general mode of feeding of cassids on its echinoid prey is that firstly, the gastropod will perch on the surface of the echinoid, holding down the spines with its muscular foot. Thereafter, the proboscis is everted and will drill a roughly circular hole on the test of the echinoid. This process may be a combination of acidic secretions, jaws and radular action of the gastropod. Upon successful etching of its prey, the proboscis will penetrate into the internal portion of the animal and consumes the flesh within by peristaltic actions of its proboscis.