Echinocyamus pusillus
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| Echinocyamus pusillus | |
|---|---|
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| Aboral view of live E. pusillus | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Echinoidea |
| Order: | Clypeasteroida |
| Family: | Fibulariidae |
| Genus: | Echinocyamus |
| Species: | E. pusillus |
| Binomial name | |
| Echinocyamus pusillus (O.F. Müller, 1776)[1] | |
| Synonyms[1] | |
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Echinocyamus pusillus, commonly known as the pea urchin or green urchin, is a species of sand dollar, a sea urchin in the family Fibulariidae, native to the northeastern Atlantic Ocean and the Mediterranean Sea. It buries itself in gravel or coarse sand at depths down to about 1,250 m (4,000 ft).
Echinocyamus pusillus is a small sea urchin with a flattened, oval body up to 15 mm (0.6 in) long. The anterior end is slightly pointed. The aboral (upper) surface is convex while the oral (lower) surface is flat. The ambulacral plates widen and form a petal-like pattern on the aboral surface, and it is through each of these areas that six to nine pairs of tube feet protrude. The whole test is clad in short dense spines, giving the living animal a furry appearance; spines of two types are present, relatively long, sharply-pointed ones and shorter ones with serrated tips. The mouth is in the centre of the oral surface and the anus is also on the oral surface but further back. The colour of this sea urchin is greenish or yellowish-grey, and it turns bright green if it gets injured.[2][3]