Found imbedded in the skin of whales and other marine animals, though
not generally at so great a depth as the Tubicinella. Shell in form a
little variable and without trace of support; the coronary part formed
of six pieces, as in those properly called _Balanus_, but more regularly
disposed in a manner to imitate a kind of crown or tube; spaces
alternately hollowed and saliant; operculum not articulated, composed of
two pairs of small, level, delicate valves, joined at the aperture of
the tube by a considerable membranous part, leaving a passage for the
cirrhous appendages of the animal.
Coronula testudinaria.
C. balænarum.
C. diadema.
C. quinquevalvis.
_C. testudinaria._ The Tortoise Coronula.
Very depressed, circular, as if radiated by the disposition of marked
spaces, striated transversely, forming six rays diverging from the
centre to the circumference; aperture oval and hexagonal.
_C. balænarum._ The Whale Coronula.
A little more elevated; the spaces prominent, equal between them, much
larger than the excavated; the aperture subcircular; the operculum of
four valves, almost equal, occupying but a small space of the membranous
part which forms between them a sort of tube.
_C. diadema._ The Crown Coronula.
More elevated, sub-hexagonal; the spaces almost equal, the hollow parts
larger than the saliant; the superior aperture very large and hexagonal;
the inferior much smaller, of the same form, and communicating in a
round excavation by radiated plates; the operculum bivalve.
_C. quinquevalvis._ The five-valved Coronula. Pl. 4, fig. 3.
Species irregular, having only five valves, of a purple hue.