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

—;452 COLLECTIONS FROM MELAXE.SIA.fibre. (4) Equianchorate ; navicular, shaft almost straight, pointedat each end ; length "OIG-'OIS millim.Hah. Port Darwin, 7-12 fms. ; bottom sand, mud, and shells.The above diagnosis is based on a large specimen. A smallspecimen (which is perhaps the apes of a larger one), 36 millim.high, also occurs from the same place and same depth, differingfrom it in having no perceptible horny fibre, in being, in consequence,soft and fiaccid, and in having the spined acuate confined to acentral axis which contains a large quantity of sand ; it is probablyidentical with the large specimen, its diff'erences being partly individual,partly due to youth ; it contains the parasite Spongiophagus,Carter. This very fine species appears to be referable toRliaplikloplilus by possessing a distinct dermal crust composed mainlyof smooth spinulate spicules with their points projected outwards,but adds to this the presence in this crust of the spined echinatingspicules, a feature in which it resembles Dlrrhopalum. The crustis thin, but appears to represent the correspondingly situated structurein R. cratitius, Esper (Ehlers). Its root-like base recalls thehorizontal meshwork figured by Esper, and here, as there, the erectportion appears to have no real tendency to form branches ; but,besides the differences in the dermis, the skeleton and echinatingspicules are both much longer than in the type and hitherto onlyrecognized species of the genus. The height of the perfect andwell-preserved spirit-specimen is 470 millim. (18^ inches). Thearborescent form, the strongly horny fibre, the slenderness of theskeletal and echinating spicules, the replacement of the spinulatefor the most part by the spined acuate in the main-skeleton fibre,and the thickness of the dermal crust, distinguish R. arborescens fromR, procerus.81. RhaphidopMus, sp.The following appears to be distinct from all known species ofthe genus, but more material is necessary for full description :A small dry specimen of subramose cylindrical growth, 45 millim.long by 12 millim. in greatest diameter, the surface proliferatinginto ridges and processes 2-3 millim. high, giving it a fiocculentappearance. Colour pale dusky brown. Skeleton UTCgularly rectangularin arrangement ; spicules united in the fibre by a smallamount of very pale horny substance, which is only occasionallyseen outside the spicules ;primary fibres about 8 to 10, secondary6 to 8 spicules broad. Dermal skeleton a single layer of smoothsubspinulates in tufts radiating outwards.Spicules :—(1) Smooth acuate, tapering gradually to sharp pointsize -23 by -0095 to -0127 millim. : in fibre. (2) Smooth subspinulate,forming dermal layer ; head very slight, larger than shafttapering gradually to sharp point ; size -25 by '0095 to -0127 millim,(3) Spined cylindrical, tapering gradually from well-rounded, veryslightly dilated base to rounded apex, which is about one thirdthe diameter of the base; spines prominent, sharp, distal ones