The sea potato is a heart-shaped urchin clothed in a dense mat of furrowed yellowish spines which grow from tubercles and mostly point backwards.

During life, the spines trap air which helps prevent asphyxiation for the buried urchin.

This organic debris is used by the buried animal as food and is passed down by means of the long tube feet found in the front of the ambulacrum.

[14] The sexes are separate in the sea potato and the males and females both liberate gametes into the water table in the spring.

[19] The bivalve Tellimya ferruginosa is often found living inside the sea potato's burrow as a commensal.

[22] According to traditional belief, the distinct patterns visible on the test are thought to resemble an apparition of the Virgin Mary.

There is also a traditional association between the appearance of the shells on beaches in West Cork and the Marian month of May and the Feast of the Assumption.