Classis Echinoidea

Bronn, 1860

Sea-urchins, Sand-dollars and Heart-urchins

Description
Free-living Echinoderms with a globular, egg-shaped or flattened body. They have a compact, mostly hard test formed by regularly arranged plates carrying tubercles with movable spines.

Tube-feet
The tube-feet are arranged in 10 meridian series, not in furrows. A double pore in the test corresponds to each tube-foot.

Mouth and alimentary canal
The intestine is long and coiled. The mouth is faced downwards towards the substratum.
The anal opening is always present.

Treated taxa:
- Order Clypeastroidea
- Order Diadematoidea
- Order Spatangoidea

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