_Shell reddish-brown, depressed, thin, finely furrowed longitudinally:
tergum with the basal margin having a slight angular bend._
_Hab._--Philippine Archipelago; rare; Mus. Cuming.
_General Appearance and Structure._--Shell circular, much depressed;
coloured brown, with an orange-red tint; surface regularly and
narrowly furrowed in longitudinal lines, the intermediate rounded
ridges projecting at the basal margin in finger-like points. The
eight compartments, when disarticulated, are of nearly equal sizes;
the carino-lateral and rostro-lateral compartments being rather
smaller than the others. The radii are neatly toothed; but with the
exception of these teeth, which are equally developed on both sides
of the sutures, and which closely interlock in the lower part of the
shell, but stand a little apart in the upper part, the radii can
hardly be said to be developed. The alæ do not form a rectangular
shoulder, the lower margin being regularly curved into the parietes;
the upper margin is only slightly oblique; the external surface
is furrowed by lines of growth. The shell increases a little in
diameter, chiefly by the growth of the alæ. The parietes are not very
thick, with the inner surface smooth, but with punctures placed in
rows for the entrance of the tubuli: the laminæ of shell alternate
with layers of yellow finely punctured membrane. Basis formed of thin
membrane, in concentric slips. Basal diameter of largest specimen, .6
of an inch.
_Scuta_ broad, with the lines of growth few in number, but extremely
prominent, so as to form folds: basal margin with a very slight
angular bend: articular ridge not very prominent. _Terga_, with a
narrow slip along the scutal margin, having the lines or folds of
growth so prominent as almost to form a series of small transverse
pits: the basal margin of this portion forms an angle with the rest
of the basal margin: no spur can be said to exist: the crests for the
depressor muscle depend a little beneath the basal margin: articular
ridge very prominent.
_Mouth_: labrum and palpi as in the last species. Mandibles with
three main teeth, apparently single, of which the lower tooth has
its upper edge pectinated: the inferior part of the mandible is
pectinated as usual. The maxillæ have two notches, one beneath the
two upper large spines, and the other in the middle, separating some
thicker and thinner spines.
_Cirri_: first and second pairs short, with the anterior rami in
each longer by about two segments than the posterior rami; all the
segments thickly covered with bristles. The third cirrus is much
longer than the second cirrus, with the posterior ramus longer than
the anterior ramus; on the latter the three basal segments, and on
the posterior ramus the two basal segments are thickly covered with
bristles; the other segments have bristles arranged as on the three
posterior pairs of cirri, namely, each segment has four pairs of main
spines, of which the two lower pairs are short.
The unarticulated support, whence the articulated portion of the
penis arises, is unusually long, equalling the pedicel of the sixth
cirrus.