Cassidae - Helmet and Bonnet Snails
Cassidae, the helmet snails (also called bonnet snails), have medium to large shells with a large body whorl, small spire and a thickened, reflected outer aperture lip. The inner and outer lips are usually toothed. The siphonal canal is generally short, narrow and twisted. Many can be found in the intertidal zone where they bury in the sand during the day and come out at night. Others prefer harder substrates or deeper water. Their favorite prey are echinoderms, especially sea urchins. The snails sneaks up on their prey, raise up high and drop their heavy shells onto the urchin. The thick skin of the snail's foot provides protection from the urchin's spines. The snail will release a paralytic enzyme that protects the snail from toxins in the urchin's spines. It then drills a hole in the urchins with a raspy tongue (called radula) aided by a secretion high in sulfuric acid and proceeds to suck out the soft parts.
Many of the shells in this family are large and beautiful. Because of their thick shell, some are used by artisans for carving cameos. There are 6 species found in Texas waters.