_Shell conical, generally smooth: when not deeply corroded of a pale
dirty flesh-colour: sutures always distinct: radii, when present, with
their sutural edges quite smooth._
_Hab._--New South Wales, (Moreton Bay, 27° S.; Sydney; Twofold Bay),
Van Diemen's Land (Hobart Town). Attached to littoral rocks and
shells; Mus. Brit., Cuming, Darwin.
_General Appearance and Structure of Shell._--Shell conical, rather
smooth; when not much corroded, of a pale dirty flesh-colour; often
covered by membrane; sometimes deeply corroded, extremely rugged,
and then of a brown colour; in this condition not much punctured,
as generally is the case with _C. stellatus_. Sutures almost always
quite distinct; rarely the shell becomes cylindrical with the sutures
obliterated. Orifice moderately elongated, sub-hexagonal. Radii
rather narrow, but not so narrow as in _C. stellatus_, smooth, with
their upper margins very oblique: when disarticulated their edges
are quite smooth. The edges of the alæ are sometimes crenated, and
sometimes not so, being only marked by lines of growth; they are
often rather thick. The parietes are usually rather thick, with their
internal surfaces smooth, and not mamillated, as is so often the case
with _C. stellatus_. The largest specimens which I have seen, were .6
of an inch in basal diameter.
_Opercular Valves._--These are hardly distinguishable from those of
_C. stellatus_. The only very slight difference which I can point out
is, that the crests for the tergal depressores are less spread out,
and depend rather more beneath the basal margin of the valve; and
lastly, that the surface of the tergum, just above these crests, is
rather prominent.
_Branchiæ_: these are oblong; taper but little, and have a broad
rounded end: they are scarcely plicated.
_Mouth._--The crest of labrum is hairy: the palpi are square, and
have no bristles along their basal exterior margins, but long ones
at their truncated ends. The mandibles have three or four main teeth
apparently single: the inferior coarsely pectinated portion is short.
The maxillæ are deeply notched.
_Cirri._--The first and second pairs, and portions of the third, are
darker coloured than the three posterior pairs. The rami in both of
the first two pairs are slightly unequal in length. The third cirrus
is much longer than the second: in a specimen in which there were
six segments in the shorter ramus of the first and second pairs,
there were twenty segments in the posterior and shorter ramus of
the third cirrus; and in this same individual there were no less
than forty-nine segments in the anterior ramus. In another specimen
(Pl. 29, fig. 2) the number of segments in the two rami of the
third cirrus, was 20 and 41; in another, the numbers were 18 and
53; in several other specimens the numbers varied in about these
proportions; but in one single specimen the numbers were equal.
Not only did the number of segments thus vary in the two rami,
but likewise the arrangement of the spines on the segments in the
anterior and longer ramus; in some specimens the spines on all the
segments were arranged in a single circle, and then the organ had a
specially antenniformed appearance: in other specimens, some of the
lower segments (in one case thirteen in number) had the spines placed
in regular pairs precisely as on the posterior ramus, and as on the
three posterior pairs of cirri. Under the genus I have pointed out
the resemblance between this structure and that occurring in certain
Macrourous Crustaceans. The pedicel of the third cirrus had its
spines more crowded and irregular than on the three posterior pairs
of cirri. The segments in the latter vary in bearing either three or
four pairs of main spines. The whole dorsal surfaces of the lower
segments of the several posterior cirri are serrated in an upward
direction by short spines, but to a variable degree.