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

—;SPOITGIIDA. 6132 millim. thick, which form the boundaries of cavities 1-2 millim.wide, extending parallel to the surface ; the intervals between thetrabeculte are more or less tympanized by thin transparent membranousexpansions. Consistency in spirit (a) of monticular specimensoft and elastic, like Turkey sponge; (6) of subcylindrical specimenstough, parchment-like. Colour — («) almost white, (h) dull putty- toreddish brown.Main skeleton— primary fibres approximately vertical to surface,•05 to '07 millim. thick, -18 to -35 millim. apart ; secondariesapproximately vortical to surface, but often curved ; size, asprimaries ; about '18 to -25 millim. apart. Dermal membrane in(«) based on fibre '035 to •! millim. thick, forming oval meshes -1 to•18 millim. in diameter ; in {h) fibre "03.5 to '088 millim. thick,meshes '14 to '3 millim. wide, oval or oblong. Fibre brown ofvarious shades, axially cored by one to four series of spicule no. 1,echinated abundantly by the spined acuate spicules.Spicules :—(1) Skeleton acuate, straight, tapering gradually fromnear centre to sharp point on the one hand and to rounded base onthe other ; base about two thirds the diameter of centre, and carryinga few very small spines ; size of spicule, -15 to -175 by '0055 millim.(2) Spined acuate, straight, tapering gradually from base to sharppoint, base rather rugose ; spines sharp, small to moderate-sized,those of proximal two thirds vertical to shaft, rather scanty, thoseof apical third numerous, recurvate ; size of spicule -075 by •0063to •OO by ^008 millim. (3) Equianchorate, navicular, shaft almoststraight, slender; palms as seen from front truncate below, subpyramidal,elongate (each more than one third the total length ofthe spicule) ; tubercle rather elongate ; size of spicule, -021 to -032millim. (4) Same as (3), but shaft more curved, and size of spiculeonly -Oil miUim.Hah. Boudeuse and Etoile Islands, Amirante group, 10-13 fms.bottom, sand or coral.The two externally very dififerent forms which I have indicatedin the description by {a) and {!>) agree so closely in their microscopiccharacters that I do not feel justified in separating them, evenvarietally ; the absence of a tough cortex from (a) is perhaps due tosome local circumstance.The greatest vertical thickness of the largest specimen is 23millim., the length 60 millim., the diameter of the lateral lobes 17millim. The brown specimens have a strong external resemblanceto small specimens of the Hippospongioi with meandrine canals,and especially to H. derasa, mihi (see Part I., p. 382, of this <strong>Report</strong>) ;also to fresh specimens of Chalinopsis clathrodes, Schmidt ; and toa specimen, now in the National collection, of an a])parently MS.species allied to CJathria, named '^ Spongia multifora, Dufr.," butwhich is quite distinct from G. decumhens, owing to the stronglyspined skeleton-spicules. The very slender slvclcton acuate with itsslightly spined head is an unusual feature in a Clathria, and fewClathrias are without either a bihamato or tricurvate flesh-spicule.The sessile massive habit distinguishes it from all other true