Teramachi’s Slit Shell, Bayerotrochus teramachii

This is a slit shell, one of fewer than thirty surviving species in an ancient family that was very abundant in all oceans from the Cambrian to the end of the Cretaceous era. The slit is a natural feature; it forms a duct that channels water out of the animal’s gill cavity. Slit shells have long been known as fossils but were thought extinct before a living one was found for the first time off the West Indies in 1879. They have since been found in South Africa, Australia, Japan and elsewhere.