longitudinal axis of the peduncle; it is narrow and internally convex;
the imbedded disc is very large, forming a continuous curve with the
upper part of the carina; this disc runs along the internal basal rim of
the scuta, and hence almost separates, internally, the peduncle from the
capitulum; it equals one fourth of the total length of the valve, and is
thrice as wide as the upper part; it is oval, externally marked by a
central line, and with a slight notch at the end, giving a divided
appearance to the whole, and indicating how easily a fork might be
formed from it. The carina is thick, measured from the inner convex to
the exterior surface, which is carinated; heel prominent.

_Peduncle_, narrow, very short, not nearly so long as the capitulum.

_Mouth._--Labrum considerably bullate, with the lower part much produced
towards the adductor muscle; crest with small bead-like teeth; palpi
small, pointed; mandibles, with the first tooth standing rather distant
from the second; inferior angle spine-like and bifid; maxillae (Pl. X,
fig. 15), with two considerable spines (only one is shown in the Plate)
beneath the upper large pair; the inferior upraised part bears seven or
eight pair of spines, and its edge is not quite straight; close to the
main notch, lying under the four upper spines, there are two minute
notches, with the interspace bearing a tuft of fine spines and a pair of
larger ones.

_Cirri._--The rami in all are rather unequal in length, the anterior
rami being rather the longest; the anterior rami of the second and third
cirri are not thicker than the posterior rami. The segments in the three
posterior cirri are not protuberant; the upper segments bear three or
four pair of spines, with some minute intermediate ones, and with the
lateral marginal spines unusually large and long, so as to form, with
the ordinary pairs, a third or fourth longitudinal row; hence a small
brush is formed on each segment. The dorsal tuft is large and wide, so
as to contain even fourteen spines, of which some are as long as those
in front. In the lower segments of these same posterior cirri, the
lateral marginal spines are not so much developed (nor is the dorsal
tuft), and hence the segments can hardly be said to be brush-like. The
first cirrus is placed rather distant from the second pair. The second
and third cirri differ from the three posterior pair, only in the
bristles being slightly more numerous, and in the dorsal tufts