GENERAL HISTOLOGY

Detailed explanation-1: -The bodies of adult sand dollars, like those of other echinoids, display radial symmetry.

Detailed explanation-2: -Like other members of its class, the sand dollar is radially symmetrical. It also shows evidence of a secondary bilateral symmetry, i.e., the mouth is centered on the oral (under) surface, but the anus lies near the rear edge of the test.

Detailed explanation-3: -Sand dollars are echinoderms and in the same phylum as sea stars and sea cucumbers. Like sea stars, they have 5-part radial symmetry. They’re covered in tube feet, which give the live animals a beautiful purple color.

Detailed explanation-4: -Radial symmetry is found in the cnidarians (including jellyfish, sea anemones, and coral) and echinoderms (such as sea urchins, brittle stars, and sea stars).

Detailed explanation-5: -Meet the sand dollar The familiar exoskeleton of a sand dollar-often found washed up on a beach-is white, with a five-pointed shape on the back that looks similar to flower petals. This design mirrors the internal structure of the sand dollar, and is called petaloid ambulacra.