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Show 350 DR. BOWERBANK ON HYALONEMA MIRABILE. [Mar. 28, Fins. The anterior extremity of the dorsal is midway between the snout and base of caudal; whilst the ventral is under its centre. Anal is situated in the posterior fourth of the body. The caudal has a broad base, and is lobed in its posterior half. Colours. Rifle-green, with a bluish-green stripe along the centre of the body and middle of the caudal fin. Abdomen greenish yellow. Fins yellow ; dorsal, pectoral, and ventral externally stained darkish. Edges of scales darker than their centres. Eyes golden. Hab. Wynaad, in rapid streams. 6. Additional observations on Hyalonema mirabile. By J. S. B O W E R B A N K , LL.D., F.R.S., F.Z.S. &c. Since my paper on LLyalonema mirabile, read January the 10th at the Zoological Society, I have been favoured by my friend Mr. Henry Lee with the loan of a specimen of that species singularly illustrative of the nature and structure of the corium, the outer coat of that organ having little or no sand or other extraneous matter imbedded in it. At the first view this singular specimen might readily be mistaken for a new species, the thin smooth corium quite destitute of sand gives it an appearance so very unlike the usual description of specimens ; but a close examination of its structural characters quickly disabuses us of this idea. The cruciform and other spicula imbedded in the corium ; the spiral column and the other structures of the basal mass of the sponge, are identical with the corresponding structures of the well-known specimens of Hyalonema. It is the absence of the usual sand which alone makes the difference between them, and at the same time greatly facilitates our knowledge of the structures of these curious animals. The whole of the corium in Mr. Lee's specimen is divided into lozenge-shaped areas of various sizes, a thin protuberant line forming the common boundaries of the adjacent areas ; at each side of this line the motive filaments are based, and from these points they pass in direct lines to the protuberant osculum in the middle of the area, passing up the sides, and on to the apex, where they terminate in a ring formed by the outer margin of the apical membrane of the osculum. The fibres are broad and flat at their bases, gradually attenuate in breadth and slightly increase in thickness as they approach their distal terminations. Two of the oscular bodies which were raised but very little above the surface of the corium, when mounted in water, exhibited the radial arrangement of the fibres in their natural condition in a very satisfactory manner : forty-four were counted ; but this was evidently not the whole of them, as many others were indistinctly apparent behind those which were counted. In another specimen in my collection which has been soaked in solution of potass I counted sixty-three; and in one of the large areas containing an osculum in Mr. Lee's specimen I counted ninety-six motive fibres, radiating from the |