Galapagos Helmet Cowry Shell, Thin Shelled Helmet Shell
Yelmo de Concha Delgada
(Cassis tenuis)

Galapagos Helmet Cowry Shell, Cassis tenuis: The Galapagos Helmet Cowry Shell has a relatively thin shell that is brown and mottled with lighter and darker spots with pale brown blotches, regular spiral ribs, and a granular callus.

They are reported to reach a maximum height of 11.0 cm (4.3 inches) and 5.0 cm (2.0 inches) in diameter. However the shell pictured below is significantly bigger.

In Mexican waters they are found in the southern half of the Sea of Cortez and south along the coast of the mainland to Guatemala.

They reside offshore and are collected by divers. Due to the size (large!) and beauty they can command in excess of $100 each via a brisk internet trade which in turn is causing a significant depletion of the population.

Note: this shell is also known in the literature as Cypraecassis tenuis.

The Galapagos Helmet Cowry 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.

Galapagos Helmet Cowry Shell picture

Galapagos Helmet Cowry Shell picture

Galapagos Helmet Cowry Shell, Cassis tenuis: Provided by the commercial fisheremen of the greater Los Cabos area of Baja California Sur, Mexico, in April 2011. Size 15.2 cm (6.0 inches) x 9.2 cm (3.6 inches). Description and photos courtesy of John Snow.