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Show 1869.] DR. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 85 were observed ; but their absence may be readily accounted for by the condition of the basal portion of the French specimen and the apparently total destruction of its dermal membrane. In every other specific character there is a complete agreement between the two specimens under consideration. Among the spicula resulting from the dissolution of a portion of the basal structures of the type specimen of D. pumiceus, I found two trifurcated expando-ternate spicula, which are represented by fig. 14, Plate III., x 666 linear. They are very minute, and probably belong to an unknown species of the genus, and were adherent to the basal membrane of D. pumiceus. I have never met with this form of spiculum before; I have therefore thought it advisable to record its occurrence. DACTVLOCALYX HETEROFORMIS, Bowerbank. Coscinospongia heteroformis, Valenciennes. Sponge sessile, fan-shaped, plicated sinuously. Surface slightly undulating, minutely hispid. Oscula on the upper surface slightly elevated and marginated, margins rounded ; uniform in size and very numerous, irregularly dispersed, rarely exceeding one-third of a line in diameter. Pores congregated on the under or inhalant surface ; porous areas scarcely visible to the unassisted eye, slightly depressed, very numerous, dispersed, rarely more than once their own diameter from each other. Expansile dermal system exceedingly ramified and complicated ; inhalant surface furnished abundantly with long, slender, flexuous spicula, irregularly dispersed amid the dermal fibres. Dermal membrane pellucid, furnished with a fine but very irregular network of apparently siliceous fibres. Skeleton -reticulations close, irregular, and very much ramified ; fibre smooth, slightly compressed ; frequently terminating in dense short tufts of minutely ramified fibres. Colour in the dried state, dark brown. Hab. Shanghai (M. Montigny, 1854). Examined in the dried condition. The sponge is composed of numerous sinuous plications or folds from 3 to 4 lines in thickness near the margin. It is 5 inches in height, 4\ inches in breadth, and, including the plications, from 3 to 4 inches from back to front. The membranous and sarcodous tissues are apparently in the same state of preservation as when taken from the sea in a living condition. The surface of the plications is slightly undulated. The hispidation of the surface is not visible to the unassisted eye; but, in a section at right angles to the surface, beneath the microscope it is distinctly apparent. The integral parts of the expansile dermal system appear to be inextricably locked together ; but this external layer of tissue is distinctly separated from the solid mass of the skeleton beneath it. The porous system on the under or inhalant surface of the sponge is a very beautiful microscopical object. The inhalant areas are exceedingly numerous and closely adjoining each other; they vary to some extent in their |