_Shell brownish, plicated; orifice twice as long as broad: tergum
triangular, equilateral, with the basal and carinal margins slightly
protuberant._
_Hab._--California, attached to _Lottia grandis_. Peru(?); Mus. Brit.
_General Appearance and Structure of Shell._--Shell globulo-conical,
irregular, with the walls much folded. Colour brownish. Sutures
generally distinct in young specimens, and nearly obliterated in
full-grown individuals. Radii, when present, very narrow. The orifice
of the shell, in full-grown specimens which have their summits a
little worn, is narrow, much elongated, about twice as long as wide,
oval or ovate, with the rostral end the narrowest: the elongation of
the orifice offers almost the only character by which this species
can be externally recognised. The lateral compartments are rather
wider than usual in proportion to the rostro-lateral compartments.
Basal diameter of largest specimen .2 of an inch.
_Scuta_, elongated transversely, with the pit for the adductor muscle
bordered on the under side by an adductor ridge rather more prominent
than usual in this genus. _Terga_, triangular, equilateral, with
the margins slightly curved and protuberant: the basal margin is
regularly and equably curved from one end to the other.
Neither the _Mouth_ nor _Cirri_ offer any peculiar characters
distinct from the genus. I may mention, however, that the crest of
the labrum is toothed, and that the segments of the posterior pairs
of cirri support five pairs of main spines.
The characters by which this species differs from _C. stellatus_ and
from the other species, consist almost exclusively in the triangular
and equilateral terga, and in the much elongated orifice of the shell;
and these differences I believe to be of specific value. I must,
however, confess that I have examined one young specimen attached to
a _Pollicipes elegans_, in which the orifice was not nearly so much
elongated, and in which the terga were not so equilateral, with the
basal margin not quite equably curved, but more protuberant on the
scutal than on the carinal side: from an examination, however, of only
one specimen, and that a young one, I cannot decide on its specific
nature.