Brachiopoda are commonly known as
the lamp shells. There are about 26 000 fossil species dating from the Cambrian onwards, but only about 350 species
Externally they are similar to the bivalve molluscs, see Terebratulina caputserpentis left.
The pedicle or ventral valve is usually larger than the brachial or dorsal valve (see right). All living species are
less than 10 cm long, though fossils can reach 30 cm long.
They attach to the surface by a stalk or pedicle, usually in a position to gain maximum benefit from the water currents.