Spongilla plumosa, Carter, J. Bomb. Asiat. Soc. iii, p. 34, pl. i, fig. 2, & Ann. Nat. Hist. (2) iv, p. 85, pl. iii, fig. 2 (1849). Spongilla plumosa, Bowerbank, P. Zool. Soc. London, 1863, p. 449, pl. xxxviii, fig. 5. Dosilia plumosa, J. E. Gray, ibid. 1867, p. 551. Meyenia plumosa, Carter, Ann. Nat. Hist. (5) vii, p. 94, pl. v, fig. 6 (1881). Meyenia plumosa, Potts, P. Ac. Philad. 1887, p. 233. Ephydatia plumosa, Weltner, Arch. Naturg. lxi (i), p. 126 (1895). Ephydatia plumosa, Petr, Rozp. Ceske Ak. Praze, Trída ii, pl. ii, figs. 29, 30 (text in Czech) (1899).
Sponge forming soft irregular masses which are sometimes as much as 14 cm. in diameter, of a pale brown or brilliant green colour; no branches developed but the surface covered with irregular projections usually of a lobe-like nature.
Skeleton delicate, with the branches diverging widely, exhibiting the characteristic structure of the genus in a marked degree, containing a considerable amount of chitin, which renders it resistant in spite of its delicacy.
Spicules. Skeleton-spicules smooth, sharply pointed, nearly straight, moderately slender, about twenty times as long as their greatest transverse diameter. Flesh-spicules occasionally amphioxous or birotulate and with a single shaft, more frequently consisting of many shafts meeting in a distinct central nodule, which is itself smooth; the shafts irregularly spiny, usually more or less nodular at the tip, which often bears a distinct circle of recurved spines that give it a rotulate appearance. Gemmule-spicules with long, slender, straight shafts, which bear short, slender, straight, horizontal spines sparsely and irregularly scattered over their surface; the rotulæ distinctly convex when seen in profile; their edge irregularly and by no means deeply notched; the shafts not extending beyond their surface but clearly seen from above as circular umbones.
Fig. 22.—Dosilia plumosa.
A=microscleres, × 240; B=gemmule as seen in optical section from below, × 75. (From Rambha.)
Gemmules. Somewhat depressed, covered with a thick granular pneumatic coat, in which the spicules stand erect; the single aperture depressed. Each gemmule surrounded more or less distinctly by a circle or several circles of flesh-spicules.
Type in the British Museum; some fragments in the Indian Museum.
Geographical Distribution.—Bombay and Madras. Carter's specimens were taken in the island of Bombay, mine at Rambha in the north-east of the Madras Presidency. I have been unable to discover this species in the neighbourhood of Calcutta, but it is apparently rare wherever it occurs.