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Show 338 DR. J. S. BOWERnANK ON SILICEO-FIBROUS SPONGES. [May 13, as to cause this genus to be readily distinguished from any others with which we are acquainted among the siliceo-fibrous sponges. KALIAPSIS CIDARIS, Bowerbank. Sponge coating, parasitical, very thin. Oscula and pores unknown. Expansile dermal system furnished with foliato-peltate connecting spicula, peltate heads more or less mammillated, very various in form; shafts short and conical. Dermal membrane furnished abundantly with minute incipiently spinous fusiformi-cylindrical spicula, short and stout, dispersed. Skeleton-basal portion composed of stout canaliculated cylindrical fibre arranged symmetrically in a series of reversed semicircular confluent arches, from the crowns of which emanate short stout cidarate prehensile fibres with acutely conical terminations. Basal limbs of the arches attenuating and ramifying irregularly upwards, and terminating at the surface of the rigid skeleton in a plane of very complicated non-canaliculated reti-form layer of depressed fibres. Colour in the dried state white. Hab. Parasitic on the base of Oculina rosea, from the South Seas (J. S. Bowerbank). Examined in the dried state. I found this singular and beautiful little sponge on the base of a specimen of Oculina rosea from the South Seas in 1855, and figured a portion of it in illustration of m y paper on the " Anatomy and Physiology of the Spongiadse" published in the ' Philosophical Transactions of the Royal Society' for 1862, plate 28. fig. 12, p. 759, as a specimen of prehensile sponge-fibre; and also in vol. i. of 'A Monograph of the British Spongiadae,' plate 15. fig. 278, p. 80, for the same purpose. I also figured seven specimens of the dermal connecting spicula in the 'Philosophical Transactions of the Royal Society' for 1858, plate 24. figs. 32-38 inclusive, in illustration of the foliato-peltate forms of connecting spicula, and described in detail the mode of their development from the simple discoid form to their mature and most complicated ramified condition. They are also figured in ' Monograph of British Spongiadse,' plate 4. figs. 102, 103, and plate 5. figs. 104-108 inclusive, in illustration of the terminology. The whole sponge, when attached to the base of the coral, did not exceed about 3 lines in diameter; and the largest portion obtained for examination is nearly square, 2 lines in length, and about 1| line in breadth, and not exceeding -fa inch in thickness. Its peculiar structure is siugularly illustrative of its parasitic habit. I have carefully examined many other specimens of Oculina rosea, but have never been fortunate enough to find another specimen. On several portions of the largest piece of rigid skeleton I found one or two of the foliato-peltate spicula adherent and in situ; and in the material scraped from the coral matrix immediately surrounding the sponge, they were found in abundance in every stage of development, and along with them numerous very minute fnsiformi- |