Description. Shell reaching about 12 mm. ( ½ inch) in length, similar in most respects to Opalia crenata, but differing by being somewhat smaller and in having the axial costae generally persisting below the basal ridge. There are 10-14 costae on the body whorl. Microscopic sculpture consisting of a very fine pitted surface, the little pits being arranged in fine spiral lines. This pitted surface is quickly lost when the shell is beach-rolled as the sculptured layer is very thin and readily suffers from abrasion. The shell appears a little more tapering with less tendency to develop a shoulder than does Opalia crenata. Operculum corneous, subcircular and paucispiral.

About 12mm, with axial costae numbering 10-14, extending below the fairly clear basal ridge. The surface is finely pitted. This species is quite like O. crenata, but differs by having the whorls unshouldered and the crenulations merging even¬ly into the whorl above, leaving pits at the suture. The species is found from south Florida through the Caribbean as far as Trinidad.

Range. Southern Florida and south through the West Indies to Trinidad.