This beautiful shell is found in fresh waters, and is distinguished from
the Cyrena by the divergent form of the primary tooth.
_G. radiata._ The radiated Galathea. Pl. 6, fig. 8.
Shell equivalve, sub-trigonal, covered with a greenish epidermis,
beneath which the surface is of a milky white, highly polished, with
several violet or pale chestnut rays diverging from the apex to the
margin; primary teeth furrowed, two on the right valve joined at the
base, three on the other valve placed triangularly, the intermediate one
being advanced, separate, thick, and callous; the muscular impressions
are lateral, and appear double on each side.