Common sand dollar
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	Echinoidea
Order:	Clypeasteroida
Family:	Echinarachniidae
Genus:	Echinarachnius
Species:	E. parma
Binomial name
Echinarachnius parma Lamarck, 1816
Synonyms
Echinarachinus parma (Lamarck, 1816) (misspelling) Echinarachnius atlanticus L. Agassiz, 1841 (subjective junior synonym) Echinarachnius australiae Michelin, 1859 (subjective junior synonym) Echinarachnius rumphii L. Agassiz, 1841 (subjective junior synonym) Echinarachnius undulatus Michelin, 1859 (subjective junior synonym) Echinodiscus parma (Lamarck, 1816) (transferred to Echinarachnius) Phelsumaster parma (Lamarck, 1816) (transferred to Echinarachnius) Phelsumia parma (Lamarck, 1816) (transferred to Echinarachnius) Scutella parma Lamarck, 1816 (transferred to Echinarachnius) Scutella trifara Say, 1826 (subjective junior synonym)

Echinarachnius parma, the common sand dollar, is a species of sand dollar native to the Northern Hemisphere. ^[1]

Subspecies

• Echinarachnius parma obesus H.L. Clark, 1914
• Echinarachnius parma parma (Lamarck, 1816)
• Echinarachnius parma sakkalinensis Argamakowa, 1934

Distribution

It is found in the North Pacific and Northwest Atlantic, on the North American east coast from New Jersey north, as well as in Alaska, Siberia, British Columbia, and Japan. It inhabits isolated areas on sandy bottoms below the low tide level down to a depth of 5,000 feet (1,500 m).

Description

The tests (shells) of these sand dollars are round, flat and disc-like, typically measuring 3 inches (7.6 cm) in diameter. The entire shell is also covered with maroon-colored moveable spines. The color is a purplish brown, becoming bleached white when washed ashore. As in other echinoderms, five radial furrows branch from the mouth on the animal's underside.

This and other species of Echinarachnius have been around since the Pliocene epoch.