2. [OCTOMERIS] BRUNNEA. Pl. [20], fig. [3 a], [3 b].
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.