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

;SPONGIIDA. 383and the greater number of cored primaries. Sponr/ia cavernosa,Esper, differs from both iu having the surface between the canalsechinated with tufts.The pecuharly smooth and unbroken character of the surface ofthe skeleton between the openings of the excretory canals appearsto be due mainly to the remarkable modification of the usual positionof the uncored primary fibres, by which, instead of running parallelto the cored primaries, and so meeting the general surface at rightangles and (as is usually the case) by a superficial projection, theyrun approximately at right angles to the very scanty cored fibres,and so parallel to the general surface of the sponge ; the very closeinterstitial network further adds to its density and evenness of thetexture.STELOSPONGUS.Stelospongos, Schmidt, Atl. Geb. p. 29 ; Hyatt, Mem. Bost. Soc. ii.pt. 3, p. 528.Polyfibrospongia, BouvrbcDiJi, P. Z. S. 1877, p. 459.Stelospongia, F. E. Schnlzc, Zeitsch. wiss. Zool. xxxii. p. 613.Stellospongia, Marshall, Zeitsch. wiss. Zool. xxxv. pp. 90, 118.I cannot see any sufficient reason for Marshall's mode of writingthe name of this genus. The first part of the word appears to bebased on (rrz/'X/j, a column, from the frequency with which Schmidtalludes to the columns (" Siiulen ") formed by the main fibres of theskeleton.6. Stelospongus excavatus. (Plate XXXIX. fig. A.)A small spirit- specimen, obtained at Port MoUe, Queensland, hasa head which arises from a short pedicel, is broad and semitruncateabove, and cup-like, being excavated on its upper surface by fourpits, the deepest occupying a great part of the thickness of the spongeeach pit contains a vent ; the vents vaiy in size from about '25 to 3millim. The colour in spirit is greyish white (putty colour) ; thedermis conceals all the skeleton but the ends of the primary fibres,which appear as low points over the whole of the outer surfaceand just inside the margins of the pits.The skeleton-liues measure about "38 millim. in diameter, theindividual fibres of primary lines from "018 to •028 millim. indiameter, those of the large secondary lines -07 millim. lioth thesecondary and primary fibres enclose more or less foreign matter,which also occurs on the outside of the primary fibres and dermis,forming a kind of mosaic. Greatest height and breadth of thesingle specimen 31 and 25 millim. respectively. Several large nucleatedand unsegmented ova are discernible in the tissues, scatteredor aggregated in groups of two or three ; the diameter of the largestis about -06 millim. ; one was also observed which had apparentlydivided into four segments.A fine dry specimen, 300 millim. in gross height by 95 iu the maximumdiameter of the cup, provided with a slender pedicel 150 millim.long, breaking up below into a number of long stringy rooting