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Show 3 1 1 DR. J. S. BOWEHBANS ON SILICEO-FIBROUS SPONGES. [May 13, case is by no means a new fact, as there are abundant instances of similar close alliances existing among the recent Australian sponges and those of the chalk formation of England ; and amongst the most prominent are the existing representatives of Choanites and Ventriculites. ALCYONCELLUM SPECIOSUM, Quoy ct Gaimard. Euplectella aspergill urn, Owen, Trans. Zool. Soc. iii. p. 203. Euplectella cucumer, Owen, Trans. Linn. Soc. xxii. p. 11/, pl. 21. Sponge sessile, cylindrical, more or less curved, enlarging progressively from the basal to the distal extremity; upper portion furnished with numerous sharp ridges of interlacing fibres disposed diagonally and somewhat symmetrically ; apex truncate, closed by a coarse, ventricose, fibrous network, and encircled by a strongly produced fibrous ridge or frill. Base furnished with numerous fasciculi of large and long prehensile spicula projected downward ; spicula at-tcnuato- quaternate, barbed alternately for about one-third of their length from the distal extremity. Oscula congregated, terminal. Pores congregated ; inhalant apertures symmetrically equidistant, disposed in lines radiating from the base to the apex of the sponge. Dermal membrane abundantly spiculous ; spicula acerate, long and slender, fasciculated ; fasciculi compact, disposed in radiating or parallel groups. Skeleton symmetrical: primary lines radiating from the base to the apex, equidistant; secondary lines at right angles to the primary ones ; interstitial structures interlacing diagonally. Spicula of the membranes-interstitial spicula rectangulated attenuated hexradiate, short and stout, rarely completely developed ; also attenuated rectangulated triradiate apically spined. Spicula of the sarcode trifurcated attenuato-hexradiate stellate, and floricomo-hex-rndiate, very minute. Colour amber-yellow ? Hab. Philippine Islands; Island of Bohol, 10 fathoms (Mr. Hugh Cuming) ; Island of Zebu, about 24 fathoms (Mr. R. Geale). Examined in the skeleton-state. There are several indications of a close alliance between Alcyoncellum and Dactylocalyx, Iphiteon, and the other genera of well developed siliceo-fibrous sponges. The structure of the skeleton-fibres and their habit of anastomosing whenever they touch each other are precisely the same as they are in the genera I have named. The floricomo-hexradiate stellate retentive spicula of Alcyoncellum, Plate XXIV. fig. 11, and the beautiful spinulo-multifurcate hexradiate spicula of Iphiteon callocyathes, Plate XXIII. fig. 7, are so peculiar in their forms, and so similar in the mode of their construction and relative positions in the two sponges, as to at once lead us to tbe conclusion that the two species are in very close alliance with each other. A similar close alliance is indicated by the comparison of the slender attenuated rec-tangulated- hexradiate interstitial spicula of Alcyoncellum (Pl. XXIV. fig. 9) and those of Iphiteon callocyathes represented Plate XXIII. |
