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Show 6 PROF. E. A. MINCHIN ON THE [May 2, The specimens of this sponge which I have studied nearly a came from Banyuls-sur-Mer, where this species is extremely abundant. By the kindness of Monsieur Topsent, however, I ha\e seen a specimen from Roscoff, not differing in any respect from the Mediterranean specimens. The sponge therefore has a wide range of distribution, and is almost certainly to be ranked as a member of the British Fauna, though it does not appear to be common on our coasts. Hanitsch has, indeed, recorded it from Liverpool: I have no reason to doubt the correctness of this record beyond the fact that my experience of specimens labelled contorta by the most eminent authorities has left me very sceptical as to the correctness of any identification of this species which I have not checked; a scepticism heightened, in the present instance, by the fact that Hanitsch names his specimens Ascaltis contorta. I may add that the sponges named Ascandra contorta by Breitfuss in various memoirs have nothing to do with this species, and should not therefore be taken into account in considering its geographical range. At Banyuls-sur-Mer Clathrina contorta is not only one of the commonest, but also one of the largest Ascons occurring there. Colonies frequently measure 8 centimetres or more across. They consist of a massive or spreading growth of twisted anastomosing tubes, running in all planes, and forming a dense feltwork from which arise at intervals the short, straight, not very conspicuous oscular tubes, which reach two or three millimetres in height, and are of slightly larger calibre than the body-tubes, as the basal growth may be called. The body-tubes are centred round the oscular tubes more or less distinctly, and in the region of the oscular tube the basal system of tubes is usually slightly raised up to form a conulus bearing the oscular tube on its summit; but these conuli are generally very shallow, so that the upper surface of the spreading colony is nearly flat, not lobulated like that of cerebrum, nor cushion-like, as in reticulum-two species occurring commonly with contorta, but both very easily distinguished from it at sight. Photographs will make the external characters of contorta clearer than any description (Plate I.). Of its allies, it is perhaps coriacea with which contorta might be most easily confused, on simple inspection ; the latter, however, with its greatly developed gastral rays, is not found contracted up, with closed oscula, like coriacea, and when expanded its body-wall is much thicker and less delicate. The spiculation of Clathrina contorta comprises in typical specimens all the three kinds of spicules found in calcareous sponges. The triradiate systems are equiangular, with the rays straight, tapering imperceptibly for the proximal half or two-thirds ; after that tapering more rapidly to a sharp or moderately blunt point (text-fig. 2, 1 a - l f ) . The distal extremities of the rays are often irregular in outline, sometimes markedly so. The rays vary in length from 80 to 130 M in different specimens, but may be said to average 90-100/,. The breadth at the proximal end of the |
