Report on the zoological collections made in the Indo-Pacific Ocean ...

.PPONGIIDA, 601its wall about •05 millim. thick, of a fine transparent pnrple colour,and is composed of a transparent matrix containing closely packedsubglobiilar transparent cells -008 to -013 millim. in diameter, providedwith small opaque refringent nuclei ; the laminae composingthe wall of the fibre are readily separated. The dermal membraneis not, as in A. membranosa, traversed by raised thickenings whichradiate from the tij)S of the conuli, but is externally homogeneousand subtransparent ; it is pale purple in colour and quite thin ;under the microscope it is subtransparent, granular and speckledin parts with the less transparent and darker purple nuclei or condensedpigment-masses, about '005 millim. in diameter, which occupythe centres of large cells.Hah. Mario Louise Island, Amirante group, 16 and 17 fms. ; ProvidenceIsland, Mascarene group, 19 fms.The species appears to be most nearly related to A. carnosa,Schmidt (Spong. Adr. Meer. p. 26, pi. iii. fig. 3), from the Adriatic,and A. cauUformis, Carter (Ann. & Mag. N. H. 1882, ix. p. 270), fromthe West Indies ; but differs from the former in its far more looselyreticulate skeleton, and from the latter in not having the surfacenearly even. It is perhaps identical with the elongated specimensdescribed by Pallas (I. c.) under Spongia membranosa. It difterssuperficially from the tj^pical form of that species in the closerapproximation of the conuli, the more slender habit of the sponge,the smoothness of the dermal membrane, in its minute structure,and in the simple, not compound, character of the skeleton-fibre.The larger specimens are slightly compressed laterally, and bothmeasure about 60 millim. (2^ inches) in height ; four spirit-specimensform the series.17. lanthella flabelliformis.Spongia flabelliformis, Tallas, Elench. ZoojyJi. p. 380.A macerated fragment agreeing in outward form, so far as it goes,and in the proportions and character of its fibre with the abovespecies. The places in the fibres originally occupied by the purplecells are chiefly represented by vacant spaces, giving a honeycombedappearance to the skeleton-fibre in some parts.Hah. Providence Reef, Mascarene Islands, 24 fms.Distribution. See Part I., p. 392, of this <strong>Report</strong>.SILICEA.MONA CTINELLIDAThe great abundance of Ceratosa has for its complement a correspondingcomparative scarcity of Monactinellid Silicca ; this deficiencyis largely accounted for by the few Ectyoriida; collected hereas compared with the Northern Australian waters.