>Ostracods are small crustaceans with the common name of water flea. They
>are common freshwater plankton and a good indicator of water quality. It is
>a shell (although not a calcite or aragonite as in mollusks) and they are
>free swimming with just feet and feelers sticking out of the shell and the
>rest of their body hidden and protected within.
Er... Daphnia (the "water flea") isn't an ostracod, though it bears
some resemblance.
--
Regards
Andrew