s under the rostrum:
valves brownish: latera regularly graduated in size from the uppermost
to the lowest: carina with the basal margin, (viewed internally,)
hollowed out in the middle: scales of the peduncle symmetrically
arranged in close whorls.

Maxillae with three tufts of fine bristles, separated by larger spines;
caudal appendages uniarticulate; filamentary appendages attached to the
prosoma.

Upper California, St. Diego and Barbara, 32 deg. to 35 deg. N.,
according to Conrad; Mus. Cuming: Low Archipelago, Pacific
Ocean; Mus. Coll. of Surgeons: Southern Pacific Ocean, collected
during the Antarctic Expedition, Mus. Brit.

_Capitulum_, but little compressed, broad, with the scuta and terga
placed in a more oblique direction, with respect to the peduncle, than
is usual, so that the line of orifice forms an unusually small angle
with the basal margin of the capitulum. The capitulum is composed of
several whorls of valves, which gradually decrease in size from above
downwards. In a medium-sized specimen there were four whorls under the
rostrum; in the lowest of these whorls, there were between eighty and
ninety valves, and in the whole capitulum from one hundred and seventy,
to one hundred and eighty. The valves in the lower whorls are not of
equal sizes. Viewed externally, the valves seem to touch and overlap
each other; viewed internally (Pl. VII, fig. 2 _a_) they are found to be
just separated from each other by transparent membrane; none of the
valves are articulated together. The outer surfaces of nearly all the
valves, except in the two last formed whorls, are much disintegrated,
and seem to be composed of alternate white and brown layers of shell.
The membrane connecting the valves, as well as that of the peduncle, (in
specimens long kept in spirits,) is brown; but in some dried specimens,
there are indications of its having been coloured crimson (as in _P.
cornucopia_), round the orifice and between the valves.

_Scuta_, irregularly oval, convex, narrow at the upper end; basal margin
may be almost said to be formed of three short, unequal margins,
corresponding with the rostrum, the rostral and the adjoining latus. The
edge corresponding with the latter, is the best marked, and is generally
slightly hollowed out, as if a piece had been broken off. The
tergo-lateral margin is curved and protuberant. The umbo projects a
little over the scutal margin of the terga.

_Terga_, projecting beyon