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: -Echinodermata (echinoderms), class: Echinoidea (sea urchins, heart urchins & sand dollars)

Detailed explanation-4: -Echinoidea is a class that belongs to the phylum Echinodermata. Species that belong to this class are the sand dollars, cake urchins, sea urchins, and heart urchins. Echinoids have an egg shaped, circular body which is hemispherical.

Detailed explanation-5: -Class Echinoidea. Sea urchins belong to the class Echinoidea, named for the movable spines projecting from their body like a hedgehog’s spines (from the Greek word echinoid meaning like a hedgehog). Sea urchins (Fig.