Family Suberitidæ
Polymastia dendyi, sp. nov.

(Plate xviii., fig. 5).

Sponge sessile, consisting of a series of mammiform processes more or less united at their bases, the upper third or half being free. The single example in the collection is 35 mm. in its long and 25 mm. in its short diameter, and about 8 to 12 mm. in height. The mammiform processes are roundly conical, varying somewhat in size; they are from 4 to 12 mm. in diameter at the base.

The sponge is pretty firm, elastic, and moderately tough, the surface has an appearance like velvet, due to the projecting stylote spicules.

The oscula are minute, and are situated in the centre of a smooth membrane at the summits of the processes. The aperture is about 0·25 mm. in diameter. The smooth membrane about 1·5 mm. The oscula margin is plain or but very slightly raised, pores not visible.

Colour in spirits light sandy gray.

Skeleton composed of numerous, slender columns of spiculo-fibre running vertically towards the surface, where they terminate in tufts of diverging spicules which project a considerable distance beyond the dermal layer, and give the surface the characteristic velvety appearance. The dense dermal layer of small spicules is about 0·3 mm. in thickness; they are somewhat irregularly dis-page 331posed, not strictly vertical to the surface as is usually the case in other species.

Megasclera—(a) Of the main body, large straight styli, a little tapering to a rounded base, and gradually tapering to a not very acute apex, many of the larger spicules which project through the dermis, are suddenly contracted at about one or two diameters from the distal extremity.

Size—About 1·5 by 0·012 mm.

(b) The small slender styli of the dermal layer have a rounded base and a tapering acute apex, a few similar spicules are found scattered throughout the body of the sponge, especially in the walls of the canals.

Size—About 0-19 by 0-0025 mm.

Reefs in the lagoon associated with Sarcophyta.