12. [BALANUS] CYMBIFORMIS. Pl. [3], fig. [5 a], [5 b].
Parietes and basis not porose. Scutum and Tergum with very small articular ridges. Tergum broad, almost equilateral.
Hab.—Attached to a Gorgonia, Tubicoreen, near Madras, (Dr. Johnston). Hab. unknown, Mus. Cuming.
General Appearance.—I have seen only two specimens, kindly sent me by Dr. Johnston, and a single specimen in Mr. Cuming’s collection. In most points this species agrees with the two last species. The shell (excepting the rostrum), and even the opercular valves in Mr. Cuming’s specimen were of a very fine purplish-red; in the other specimens they were feebly tinted purple. The parietes are strongly ribbed internally, and are not permeated by pores. The basal cup is not porose, but its inner surface is ribbed in lines radiating from the centre, and in both these respects this species differs from the two foregoing. The Radii are rather narrow; they are paler coloured than the parietes; they have their sutural edges plainly crenated. The alæ have extremely oblique summits; the narrow rim added during the diametric growth of the shell is white, the rest of the sheath being, in Mr. Cuming’s specimen, finely coloured like the parietes. Basal diameter of the longer axis of the largest specimen, .4 of an inch.
Scutum, rather narrow, with the basi-tergal corner much rounded off; externally the lines of growth are little prominent. Internally, the articular ridge is extremely little developed, and not at all reflexed; there is no adductor ridge; there is a minute pit for the lateral depressor muscle, placed almost on the edge of the valve. The Tergum is broad, forming (the spur being excepted) an almost equilateral triangle. The articular ridge is remarkably little prominent, and placed close to the scutal margin. The spur is nearly half as broad as the valve, with its extremity or basal margin in one case obliquely truncated, and in another case nearly square.
Animal’s body unknown.
13. [BALANUS] NAVICULA. Pl. [3], fig. [6 a]-[6 d].
Parietes and basis not porose: carino-lateral compartments very narrow, and of nearly the same width from top to bottom: radii with their sutural edges smooth. Scutum externally striated longitudinally.
Hab.—Attached to Gorgoniæ, Tubicoreen, Madras (associated with [B. calceolus]), Dr. Johnston. Hab. unknown, Mus. Brit. and Darwin.