Dendropoma annulatus (or irregularis)
Worm Shell. Members of this family, Vermetidae, have unspiraled
shells which are plastered to rocks and old coral. This small species,
which is usually less than a centimeter, can be very abundant in tide pools
and on rocks in the lower intertidal area. The operculum, which usually
appears as a black spot, is often more conspicuous than the shell. A larger
species (D. irregularis), occurs in enormous numbers on the "boiler
reefs" of the south shore.