and
cirri prehensile.

Swan River, Australia, attached to a coralline; Mus. Cuming.
Port Western, Bass's Straits, as stated in the Voyage of the
Astrolabe. Mus. Brit.

HERMAPHRODITE.

_Capitulum_ formed of 13 valves; namely, two scuta, two terga, a carina
and sub-carina, a rostrum, a pair of upper latera, and two pair of lower
latera; these latter valves, with the sub-carina and the rostrum, make a
whorl of six pieces. The upper part of the capitulum is, as usual,
produced. The upper valves are separated (in specimens which have not
been dried) by rather wide interspaces of membrane; they are covered
(excepting, generally, their umbones,) by membrane, which in the
interspaces is clothed with fine spines. The spines, or the marks where
they were once articulated, are visible over nearly the entire surface
of the membrane covering the valves. The spines are particularly
numerous round the orifice of the sack. The whole capitulum, (in a dried
condition), is coloured dull purplish-red, which is only in part due to
the underlying corium, for the valves themselves are pale red. After
having been long kept in spirits, the whole capitulum becomes
colourless. The valves are smooth, faintly marked by lines of growth.
The umbones of the lower valves project outwards, giving a denticulated
appearance to the base of the capitulum.

_Scuta_, slightly convex, oblong, breadth about two thirds of the
length, almost quadrilateral, with the upper portion produced into a
flat projection; this projection is almost spear-shaped, being
constricted a little on each side below the apex. There is a deep pit
for the adductor muscle. The umbo is near the apex, the part above not
being above one fifth of the whole length of the valve. As in _S.
vulgare_, the growth is at first downwards, and subsequently a little
upwards and downwards, thus producing the upper, small, spear-like
projection, which lies at a lower level than the umbo. There is a fold
on the occludent margin.

_Terga_, large, flat, triangular; carinal margin slightly hollowed out;
occludent margin slightly arched, with a small portion protuberant to a
variable amount. The apex is slightly curved towards the carina.

_Carina_, long, internally deeply concave, angularly bent, the lower
portion slightly longer and wider than the upper part; the two halves
meet each other at about an angle of 135 deg.; the upper half is parallel
to the longer axis of the terga, betwe