The common sand dollar is the skeleton or test of a marine
animal. By the time the test washes up on the beach, it
is missing its velvety covering of minute spines and has
a somewhat bleached appearance due to its exposure to
the sun. Sand dollars are in the Echinoid class of marine
animals. When alive, one species, Echinarachnius parma,
is outfitted in a maroon-colored suit of moveable spines
that encompass the entire shell. Like its close relative
the sea urchin, the sand dollar has five sets of pores
arranged in a petal pattern. The pores are used to move
sea water into its internal water-vascular system, which
allows for movement. A number of sand dollars on a seabedSand
dollars live beyond mean low water on top of or just beneath
the surface of sandy or muddy areas.
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