Coarctata Helmet Shell, Cassis coarctata: The Coarctata Helmet Shell is a brown shell with molted lighter and darker spots with an aperture that is contracted posteriorly.
They have five subtle ribs each with regular rows of large knobs. The outer lip is not thickened but has teeth.
They reach a maximum height of 4.5 cm (1.8 inches) and 2.5 cm (1.0 inches) in diameter.
In Mexican waters they range throughout the Sea of Cortez and south along the coast of the mainland to Guatemala.
They live in sandy mud and are found mostly offshore but are occasionally found in beach drift especially in the northern portions of the Sea of Cortez.
These shells are sold on a limited basis by shell collectors.
The Coarctata Helmet Shell is a member of the Cassididae Family, which are known as Helmet Shells. They have thick, heavy, solid shells with shiny porcelaneous texture, medium to short spires and an inner lip that is covered with a wide flat shelf-like callus. They have operculums that are semi-circular with radial striations. The snails are active predators feeding primarily on sea urchins.