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

598 COLLECTIONS FROM THE "WESTERN INDIAN OCEAN.Bowerbank, but differing in its very dense and opaque dermis, andthe strictly Dysidean distribution of its foreign bodies, viz. only inthe skeleton-fibres. The primary fibres arc either single or multiplein the same conulus, and range from about '07 to -36 millim. indiameter. The sponge forms low, longitudinally-extended masses,about 50 millim. (2 inches) in greatest length, 12 millim. in greatestvertical thickness, throwing out rounded lobes which are 15 millim.in greatest diameter. Vents round, few, placed near ends of lobes,1 to 2-5 millim. in diameter. Texture in spirit rather elastic, compressible.Conuli sharp-pointed, usually connected by radiatingridges with each other; height '75 to 1 millim., distance apart 1-2millim. Dermal membrane very dark grey, glabrous. Primaryfibres, as such, apparently existing only in the conuli, and not extendingbeneath them into the mass of the sponge ; secondary fibresalso very slightly developed, except in the ridges connecting theconuli, where they form a dense network of horizontal fibres, extendingto a depth of about 1 millim. below the surface. Skeletonfibres"05 to '18 millim. thick ;generally compact in structure,exhibiting no horny substance to view.Hab. Mozambique, between tide-marks (on back of crab) ; ProvidenceIsland, Mascarene group, 19 fms. (on rock).Carter's species D. Jcirki, from Mauritius, South Australia, andthe Cape of Good Hope, above cited, may possibly include this ; butas from his description and specimens it is evident that he groupsmore than one species together, and as the present form is decidedlydistinct from Bowerbank's D. Tcirli (from the far smaller diameterof the largest skeleton-fibres), it is not necessary to pursue thequestion further. The very tough and opaque dermal layer and theremarkable development of the secondary or horizontal fibre-system,which assists in producing it, distinguish this Dysklea from allintelligibly described species. Sponrielki elegans, Nardo, as describedby F. E. Schulze, appears to approach it in the fasciculated arrangementof the primary fibres, the proportions of the conuli, and thegeneral shape, but differs in its pale colour and in having the secondaryfibres more or less free from sand.OLIGOCERAS.Schulze, Zeitsch. wiss. Zool. xxxiii, p. 34.This genus, introduced (and rightly, as it seems to me) by Marshallinto this family, is based on a species from the Adriatic,remarkable for a habit of attaching to itself foreign bodies of somesize. Prof. Schulze has expressed to me verbally a doubt as towhether the genus will prove to have been rightly established. If,however, this is due to the supposition that Oligoceras is a youngstage of a horny sponge, I think it may be set aside * by a consi-* Since writing the above, I have been assured by Di*. Polujaeff, whose <strong>Report</strong>on the ' Challenger ' Ceratosa is in the press, that he has found the skeleton of