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

462 COLLECTIONS FROM MELANESIA.frond, though only curved somewhat to one side in the plane ofexpansion, was in life decumbent, so that the terminal brancheswere then in contact with the sea-bottom. The species differs fromR. australlensis in the branching and anastomosing habit and theflattened knife-edged branches, and in having the longitudinallyarranged spicules not confined to the axis, but extending to thecortex. From R. syringella, Schmidt, it also differs in its growth(though Schmidt mentions that the branches of R. sj/ringella sometimesunite) and in the absence of heads to the acuate spicules.AXINELLID^.Axinellida, Carter, An7i. ^ Mag. N. H. 1875, xvi. p. 133.This family differs from the Ectyonida) in the much greaterimportance of size of spicule as a factor of specific distinction. Therelations of the two families, however, require readjustment onmore satisfactory bases than at present.90. Axinella echidnsea. (Plate XLIII. fig. a.)? Spongia echidnaja, Lamarck, Ann. Mus. Hist. Nat. xx. p. 448.It seems likely that this will prove to be Lamarck's species.That author refers (?. c.) to Seba (Thesaurus, iii. pi. xcix. fig. 7) inillustration of his sponge. This figure has a strong resemblance tothe present species, but does not show the same tendency to lateraljunction between the branches, and has most of the latter somewhatenlarged at the tips, whereas in these specimens they usually, thoughnot invariably, are either of about the same diameter throughoutor else taper to points. The dark reddish-brown colour of thesespecimens and the peculiar echination of their surface by angularwedge- or knife-shape processes about 2 to 4 millim. high, projectingoutwards and somewhat upwards, are decidedly indicated in thefigure. In texture the specimens are tough, elastic, harsh to thetouch in the dry state ; the surface- processes are flexible, almostsoft, in spirit. In structure it is a true Axinella, and thus doesnot support Lamarck's surmise that it might be identical withSpongia muricata of Esper (Pallas, sp.), which is Tricentrium muricatumof Ehlers. The main skeleton exhibits the usual longitudinallyelongated meshes of loose spiculo-fibre, which in the stem iscomposed in part of a transparent and almost colourless horny unitingmaterial, which seems to be wanting in the surface-tufts ; distancebetween longitudinal lines of axis "07 to "1 millim. Surface coveredwith a fuscous-brown subopaque pigment, which penetrates to aslight distance below. Sarcode transparent, almost colourless, verypale reddish brown. Spicules :—(1) Smooth, slightly curved acerate,tapering gradually to sharp points, or more or less blunted atone or both ends ; size -3 by '0095 to -44 by •0127 millim. : these