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

422 Collections from Melanesia.rather brittle, white, marked (at any rate on the stem) on its innersurface by closely-sefc elongate or reticulate ridges ; covered by athin, wrinkled, paper-like, pale yellow-brown membrane. Branchesgiven off' towards end of stem, in succession, in one plane ;7-8millim. in diameter at bases, slightly less towards apices, 25 to 60millim. (1 to 2j inches) long; cylindrical at base, becoming compressedat apex into flattened subcircular or knife-like expansions, about10 to 12 millim. in width and l-o millim. in thickness ; the free endsoften (if not always) imperforate. Skeleton of cortex a rather closeHalichondrioid network, with meshes "OT-'l-l millim. wide, fibre3 to (i or 7 spicules broad. Main skeleton below cortex coarselyreticulate with immense aggregations of spicules into coarse spiculonbre.Sarcode in axial tissues brown, transparent, in cortexalmost colourless. Spicules smooth acerate, tapering gradually tosharp points from about seven diameters from ends ; size '22 by 'OOQSmillim.Hah. Thursday Island, Torres Straits, 4-5 fms. ; bottom mud.A single specimen, 175 millim, (7 inches) long, composed of twolaterally fused specimens. One end is broken across, and shows theinterior to be filled with flocculent spiculo-tissue ; it is thus doubtfulwhether this end bore any tubes. This species differs, in its verydrawn-out form, from all the described species except, perhaps,Phlceodictyon liondurasense , which is known only from a tubularfragment ; but the spicules of that species are considerably smallerthan those of this form, viz. only -16 by '008 millim.No Chalinoid or even Esperia-\\kQ fibre appears to occur in anypart of the sponge.57. Rhizochalina canalis.(Plate XXXIX. fig. F ; Plate XLI. fig. r.)Simple, unbranched, cylindrical tubes, straight or slightly bent nearmiddle. Diameter at middle about 10 millim. (in large specimens),gradually (sometimes very slightly) decreasing towards ends ; endsfinger-like, closed, 3 to 4 millim. broad. Surface somewhat uneven.Vents apparently represented by circular perforations of cortex,•5 to "8 millim. wide, few, scattered. Cortex in dry state hard, ratherbrittle, slightly compressible towards ends, dense ; colour greyish ;thickness about '7 millim. ; outer layer hard, about '2 millim. thick ;inner layer bast-like, closely reticulate, about -3 millim. thick. Axialsubstance ? Skeleton of cortex composed of very strong verticalspiculo-fibres 5-12 spicules broad, interlacing closely at the surfaceto form the hard outer layer ; they are about '14 to -18 millim. apartand about "7 millim. long at the thickest part of the cortex, beingmet at their inner extremities by a strong secondary fibre (parallelto the surface) about 10 spicules broad. Sarcode pale brown, transparent.Spicules smooth acerate, becoming rounded off (rather thantapering) to sharp points from about four diameters from ends ; size•27 by -014 millim.