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Show 1869.] DR. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 77 ALCYONCELLUM, Quoy et Gaimard. Sponge fistulate ; fistula single, without a massive base. Skeleton siliceo-fibrous; primary lines radiating from the base in parallel straight or slightly spiral lines; secondary lines at right angles to the primary ones. Oscula congregated, with or without a marginal boundary to their area. Type Alcyoncellum speciosum, Museum Jardin des Plantes, Paris. D A C T Y L O C A L Y X P U M I C E U S , Stutchbury. Sponge cyathiform, slightly pedicelled. Surface even. Oscula and pores unknown. Expansile dermal system-connecting spicula furcated, attenuato-patento-ternate, and dichotomo-patento-ternate. Dermal membrane-tension-spicula small acerate and subequiangular triradiate spicula; retentive and defensive spicula acerate or cylindrical verticillately spinous, whorls of spines numerous and very large; and also attenuato-stellate, very minute, and numerous. Skeleton :-rete irregular ; fibre stout, irregularly and abundantly tuberculated, apices of the tubercles minutely papillous. Auxiliary skeleton-fibres more or less rectangular hexradiate, profusely spinous, distal terminations clavate, large and numerous. Tension-spicula rectangular hexradiate, smooth, long and slender, radii subclavate. Retentive spicula trifurcated attenuato-hexra-diate stellate ; and spinulo-trifurcated hexradiate stellate, minute and very numerous. Gemmules membranous, aspiculous. Colour unknown in the living state. Hab. Barbadoes (Dr. Cutting), " Martinique par M . Ple'e, 1829." Examined in the state of skeleton. Stutchbury's paper descriptive of this sponge was read at the Zoological Society, Oct. 26, 1841, and was published in vol. ix. p. 86 of their Proceedings. A full account of the paper is also published in the 'Annals and Magazine of Natural History,' vol. ix. p. 504. The author describes the sponge as being " formed entirely of silex, the reticulate structure of the mass being composed of transparent vitreous tubuli without any admixture of keratose or calcareous matter." This is a mistake, as the adult fibres are solid in every portion of them from the type specimen that I have submitted to microscopical examination. Stutchbury has characterized the species as follows :- '' Sponge fixed, rigid, siliceous ; incurrent canals uniform in size ; excurrent canals large, forming deep sinuosities on the outer surface, radiating from the root to the outer circumference." In this description the author has reversed the positions of the inhalant and exhalant organs, the former being placed on the outer surface and the latter on the inner one. The whole of these characters appertain only to its outward appearance ; and the description would serve equally well for several other species beside the one to which he has applied it. I have therefore thought it necessary to characterize the sponge from its internal |