heart urchin

noun

1. an echinoderm of the order Spatangoida, having an elongate, somewhat heart-shaped outer covering.

heart urchin

noun

1. any echinoderm of the genus Echinocardium, having a heart-shaped body enclosed in a rigid spiny test: class Echinoidea (sea urchins)

Word History and Origins

Origin of heart urchin¹

First recorded in 1835–45

Example Sentences

According to the Cornwall Wildlife Trust, the sea potato, which is also known as a heart urchin, lives buried in up to 15cm of sand or muddy sediment.

From BBC

The nocturnal sea mouse, four centimeters long, is a kind of heart urchin with thin spines that can hurt a diver digging in the sand for it. 

From New York Times