um_
are larger than the largest of the latera; their inner surfaces are
transversely elongated, rounded at both ends, and slightly concave;
externally they are pointed, and project outwards; sometimes the
sub-carina, and sometimes the sub-rostrum is the largest.

_Latera_, small, with their inner surfaces transversely elongated, the
larger being the most elongated. Externally they are acuminated, and
directed upwards; they project but very little beyond the thick membrane
in which they are imbedded. Neither the number, size, nor shape of the
latera agree on opposite sides of the same individual; and it would
appear that, occasionally, some of them cease to grow, and disappear. In
the large specimen with only thirty-one valves, the three pairs of
latera, corresponding to the upper, rostral, and carinal latera in
Scalpellum, were larger in a marked manner than the others; but in the
specimen with fifty-four valves, this could hardly be said to be the
case. In this latter specimen, some of the valves in the lowermost whorl
were exceedingly minute.

_Peduncle_, broad, about as long as the capitulum; surface of attachment
wide; calcareous scales minute, placed in transverse rows, which become
less and less regular in the lower part. The scales do not stand very
close together; they are of unequal sizes and irregular outline;
generally spindle-shaped; calcareous matter is added regularly only to
the scales in the uppermost row, and irregularly to some of the lower
scales. The latter, consequently, are the largest, and often much
elongated; they are sometimes of singular and irregular shapes.

_Colour._--The membrane covering the valves and forming the peduncle,
(after having been long kept dry, and not having been in spirits,) is
dark reddish chocolate-brown; corium of sack dark purple; cirri banded
with dark purplish-brown, with the lower parts of the trophi similarly
coloured.

_Filamentary Appendages_, none, but on the prosoma there are scattered
some small papillae, which are roughened by finely spinose scales, like
combs; these papillae certainly seem to represent the filaments in
_Pollicipes cornucopia_ and its two allies.

_Ovigerous Fraena_, seated in the same position as in _P. spinosus_, but
rather longer, with an elliptical _tuft_ of glands on the crest.

_Mouth_, not placed far from the adductor muscle.

_Labrum_, moderately bullate, with the upper part not overhanging; no
teeth on the crest. _Palpi_, shor