GENERAL HISTOLOGY

Detailed explanation-1: -Sea urchins and sand dollars are examples of Echinoidea. These echinoderms do not have arms, but are hemispherical or flattened with five rows of tube feet that help them in slow movement; tube feet are extruded through pores of a continuous internal shell called a test.

Detailed explanation-2: -Sand dollars belong to Phylum Echinodermata and Class Echinoidea which includes sea urchins and heart urchins. Features: They got their name because they resemble a one-dollar coin. Like other echinoderms, sand dollars are symmetrical along five axes, and have tube feet and spines.

Detailed explanation-3: -Sand dollars are echinoderms, related to sea stars and sea urchins. Like all echinoderms, their bodies are based on five-part symmetry (watch our video on the body plan of these animals: Five part symmetry).

Detailed explanation-4: -Irregular echinoids are the sand dollars, which are generally found on sandy or soft ground. Like all echinoderms, echinoids are pentaradially symmetrical, have a water-vascular system, and have an internal skeleton made of calcitic ossicles (plates).

Detailed explanation-5: -Sand Dollars are members of the phylum Echinodermata, and their relatives include sea cucumbers, sea stars and sea urchins among others. Characteristics of this phylum include spiny skin, tube feet for locomotion, and radial symmetry.