This shell is found in the Icy Sea, and on the coast of Canada, and
attains the length of seven inches. The animal of the Pyrula is at
present unknown. There is a kind of keel or ridge along the edge of the
whorls, which is obliterated in very old specimens. There are as many
as eight-and-twenty species of this shell.
[Illustration: _Turbo marmoratus. Pleurotoma babylonia. Trochus
imperialis._]