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

:;440 COLLECTIONS FROM MELANESIA.shallow depressions, covered by a glabrous semitransparent membrane,rendered rough by the projection of the low ends of theprimary fibres, •25 to '5 millim, apart (many smooth patches occur) ;texture in spirit brittle, compressible (specimen No. 1), rather tough,elastic (specimen No. 2); colour pale greyish (specimen No. 1) orreddish brown (specimen No. 2). Internal structure cavernous,loose. Vents numerous, scattered, circular or oval, leading deeplyinto sponge ; diameter 1-5 to 3 millim.Main skeleton regular, rectangular ia arrangement ;primaryfibres set at right angles to surface, '18 to '35 millim. apart, OlSto '03 millim. thick ; secondary fibres at right angles to primaries,•18 to ^35 millim. or upwards ajjart, similar to primaries in proportions; fibres wholly composed of foreign bodies united by an almostcolourless, not dense, substance. Dermal skeleton formed by smallforeign bodies scattered abundantly over the dermis, tending toaggregate into slightly denser anastomosing tracts about "14 millim.broad, enclosing rounded meshes about ^18 to ^53 millim. in diameter,and by the cylindrical spicules of the sponge, which by looseaggregation form tracts, about 4 to 6 spicules broad, below theskeleton of foreign bodies, the tracts branching and anastomosingnot unfrequently, and ending freely on the surface in slightlyexpanding tufts ; sarcode subtransparent, granular, colour a warmbrown (slightly in specimen No. 1 , strongly in specimen No. 2, inwhich it is more dense. Spicules:—(1) Slender acerate, smooth, withvery slightly enlarged subpyriform basal end, the other end ratherbluntly pointed ; size about •IG to •lO by •0021 by ^0032 millim.forming part of dermal skeleton and scattered over main skeletonfibres.(2) Contort bihamate, smooth, curve moderately strong,points sharp, suddenly and sharply bent inwards ; size ^032 by ^002millim. : abundant in subjacent tissues. (3) Tridentate equiauchorate,shaft well curved, about "0016 millim. thick ; teeth slender,sharp, curved inwards, about "008 millim. long ; spicule ^022 millim.long. Foreign bodies small in specimen No. 1 ; large, for the mostpart, in specimen No. 2.Hab. Specimen No. 1 : Prince of "Wales Channel, Torres Straits,7-9 fms. ; bottom sand. Specimen No. 2 : Port Jackson, 0-5 fms.Two specimens in spirit. No. 1 has apparently been torn from alarger mass ; it is much penetrated by some thin Algas, on which itseems to have grown much as Amorphina panicea grows over weedit measures 60 millim. by 22 millim. in its two chief dimensions.No. 2 is somewhat compressed on one side, and measures 36 by19 by 12 millim. The anchorate spicule is scarce in one of thespecimens (that from Port Jackson), while it is abundant in theother.The variability in colour and texture, and i)erhaps in the secondaryfibres, is considerable, but not surprising, considering thedistance between the stations at which the specimens were obtained ;in other points the agreement is close. The species is a very distinctone, differing from both Marshall's species in the presence ofa well-defined reticulate skeleton and of an anchorate flesh-spicule.