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Show 1873.] DR. J. S. BOWERBANK ON THE SPONGIADcE. 19 long ray is projected among the interstitial membranes at about right angles to either the dermal or the cloacal surface. The space between the cloacal and the dermal strata seldom exceeds the length of two long radii as projected from the opposite surfaces, their apices meeting and being cemented together by keratode. There are no interlacing spicula connecting these slender compound columns, the dense case of strong acerate dermal spicula affording sufficient protection and support to the delicately constructed interstitial tissues. DESMACIDON FISTULOSA, Bowerbank. (Plate IV.) Sponge massive, sessile (?), furnished with long, slender, external, fistulous cloacee. Surface smooth and even. Oscula and pores inconspicuous. Dermal membrane coriaceous, abundantly spiculous ; spicula thickly but equably dispersed, same size and form as those of the skeleton. Skeleton-fibrous rete stout, elongately diffuse, most abundant near the external surface; interstitial rete regular, unispiculous, areas rarely exceeding the length of one spiculum in width; skeleton-spicula of both parts acerate, rather short and stout. Colour in the dried state fawn-yellow. Hab. Fremantle, Australia (George Clifton, Esq.). Examined in the dried state. I received two specimens of this remarkable species from m y friend Mr. George Clifton. The one figured is rather the smallest of the two ; but the form of the bulbous mass of the sponge is as nearly as possible the same in both. In the figured specimen there are four large cloacae remaining; and two others have formerly existed, but have been rubbed off close to the dermal surface and their orifice healed over. O n the second specimen nine fistulous cloacae are projected from the distal surface; they are less in diameter than those of the figured one, and none of them exceeds an inch in height. There is a remarkable coincidence in the condition of the basal portions of the two specimens : each of them has undergone abrasion to such an extent as to have totally destroyed the dermal membranes of those parts, as if they had been freely floating about on a coarse sandy surface. On neither of them is there any indication of their having had stout root-like appendages for attachments; and the abraded surfaces consist of interstitial reticulate structure without any admixture of the stout spiculo-fibrous skeleton. The dermal membrane in its present state has a very coriaceous appearance, and on some parts of the surface it is wrinkled by drying, much like very-thin leather under similar circumstances. It is rather thick and is abundantly spiculous ; the spicula are short and stoiit, of the same size and form as those of the skeleton. They are thickly and irregularly but equably dispersed. The fibrous portion of the skeleton prevails more especially near the dermal surface; and the fistulous cloacae are composed almost entirely of it-long lines of primary fibres parallel to each other,. connected by secondary ones at nearly right angles to the primary |
