Common sand dollar

Appearance

The tests of these sand dollars are round, flat and disc-like, typically measuring 3 inches 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.

Naming

;Subspecies:
⤷  "Echinarachnius parma obesus" H.L. Clark, 1914
⤷  "Echinarachnius parma parma"
⤷  "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.