Definitions for "Echinoids"
Radially symmetrical marine invertebrates that have spiny, calcite plates, such as urchins and sand dollars
Group (class) of echinoderms including sea urchins, heart urchins, sand dollars, etc. They are spiny and globular to disc-like in shape.
A group of marine invertebrates which lived on and and beneath the sea bed. Some species are characterised by the presence of spines protruding from a spherical shell, others lived beneath the sea floor, feeding on organic materials trapped within the sediment.