spur-shell

from The Century Dictionary.

• noun A shell of the genus Imperator (formerly called Calcar): so named from its resemblance to the rowel of a spur. The term extends to some similar trochiform shells. See cut under

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) Any one of several species of handsome marine gastropod shells of the genus Trochus, or Imperator. The shell is conical, with the margin toothed somewhat like the rowel of a spur.