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

SPONGIIDA. 475simply grey. A distinct cortical layer, containing the subcorticalcrypts, and formed in adult specimens by the space between theheads of the zonc-spicules and those of the anchors, diameter about7 millim. ; sarcode here of same consistency as in rest of sponge.Sponge-sarcode below surface rather dark yellow-brown, rathergranular; that of surface (in well-preserved specimens) reddishbrown, granular.Spicules :—(1) Zone-spicule, with long shaft tapering graduallyfrom head to sharp point ; head composed of three bifid arms ; theproximal third of each arm projects forward at an angle of about120° to the shaft, and then bifurcates in a plane parallel to that ofthe surface of the sponge, so that the ultimate divisions are parallelwith this surface ;the ultimate divisions taper gradually to sharppoints from the point of bifurcation ; shaft about 3 millim. long by•035 millim. in diameter ; total length of single arm '32 millim., ofproximal (simple) part •! millim. ; diameter of proximal partthroughout •028-"032 millim., of base of ultimate divisions aboutthe same. (2) Anchor, with long shaft tapering gradually fromhead to sharp point, and head composed of three arms taperinggradually to sharp points, curved backwards to form angles of about45° with shalt (the angles vary slightly in different specimens) ; shaftabout 2-1 millim. by '022 to -024 millim. ; expanse of arms -ll to•12 millim., diameter of arm at base about -02 millim. (3) Bodyacerate, long and slender, smooth, tapering gradually to sharppoints from the centre ; size about 3 by '025 millim. (4) Fleshspicule,composed of about 7 to 12 straight arms, radiating from acentre which does not show any perceptible inflation ; arms veryslender (about -0008 millim. in diameter), terminated by heads ofabout twice their own diameter ; spicule '01 to 'OlS millim. indiameter across the arms : distributed generally in sarcode.Hab. Prince of Wales Channel and West Island, Torres Straits,7-9 fms. ; bottom sand and coral. Arafura Sea, off N.W. coast ofAustralia, 32-30 fms. ; bottom sand, mud, and shells.This appears to be a small species, none of the specimens exceeding13 millim. in their longest diameter. It exhibits, as comparedwith aS'. pm-purea^ a remarkable constancy in its form andin the occurrence of a vent, and the spicules vary but slightly inform and dimensions (the only variations observed are incorporatedwith the description above). In Torres Straits very fewspecimens were obtained ; but in the Arafura Sea a considerablenumber of small specimens occurred. Stelletta clavosa differsfrom all nearly allied forms excej)t S. tethyopsis^ Carter, in thebifurcation of the arms of the zone-spicule, and from the latterspecies by the absence of " anchors " and of an external as distinguishedfrom an internal form of stellate. The arms of the zonespiculeare much longer in proportion to their thickness than inCarter's species.Parasite. In the superficial sarcode (probably just beneath theectoderm) of one specimen occur a large number of a chain-hkeAlga, resembling Nostoc, usually coiled, with very distinct cells.