OCR Text |
Show 1906.] ALCYONARIANS FROM ZANZIBAR. 409 stand. Between the larger meshes there are smaller ones on which young polyps are seen. The polyps are about 5 m m . in length, with tentacles of 1*5 mm., with about 8 short pinnules in a single row on each side. On the lower part of the polyp-body there are no spicules, but just below the base of the tentacles spicules become abundant, at first arranged transversely, then in more or less regular converging double rows running perpendicularly. There are also a few small irregularly-disposed spicules in the tentacles. This species closely approaches Sympodium (Alcyonium) fulvum Forsk., but differs in that the upper part of the polyp has no transverse ring of spicules markedly different in size from the longitudinally-disposed spicules, in the presence of spicules on the tentacles, and in other features. Loccdities. Wasin, Chuaka, Kiungani. Common. SYMPODIUM SPLENDENS, sp. n. (Plate XXIX. fig. 8.) A beautiful purplish-crimson colony, spreading around a mon-axonid sponge. The sponge has a tubular form (probably due to some foreign axis which has been lost). The basal membrane is about 2 m m . in thickness ; the polyps occur irregularly, sometimes almost touching, elsewhere separated by intervals of 4 m m . or so. A fully-extended polyp is 3-3*5 m m . in length ; the tentacles extend for 2-2*3 m m . further; the average breadth of a polyp is 1*75 m m . When the polyp is completely retracted we see a blunt conical calyx (often 2*5 m m . in height), with 8 longitudinal ridges not very sharply defined, and ending in 8 triangles. The whole is purplish crimson, except at the summit, where a hint of the yellowish - white polyp is seen. The fully-expanded polyp is almost transparent, for the coloured spicules are not continued beyond the calyx. The flat tentacles have a broad bare streak on each surface; there are two rows of pinnules on each side, 20-24 in each row. There is great variety in the spicules :-(a) Straight and curved spindles with prominent warts, usually few and distant, sometimes fairly numerous (0*4 x 0*04, 0*35 x 0*03). (b) Irregular forms: triradiate (0*175x0*15), quadradiate (0*2 x 0*125). The great majority are purplish; others are transparent, with a considerable organic residue, a few incline to red. Locality. Chuaka. Family TUBIPORID^E. TUBIPORA CHAMISSONIS Ehrenberg. (= Tubipora musica Cha-misso.) Locality. Large colonies are abundant wherever coral grows : e. g., Prison Island and the reefs south of Zanzibar Harbour, edge of eastern reef of Pemba. Not found at Chuaka, rare at Wasin. |