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

SPONGIIDA. 367tremcly short, and deal almost invariably with the mere externalcharacters of the forms to which they refer, and thus, owing to thewell-known variability and comparatively slight diagnostic importanceof these characters in the Spongiida, are almost useless, per se,even for the identification of species.Thus we have in all some 90 species (allowing for synonyms},more or less fully described, of Sponges chiefly from the southern,south-eastern, and south-western coasts of Australia, and some 60species described in the barest manner, probably (but not certainly)in most cases from the northern coasts, and a few from the south.The present collection comprises upwards of 300 specimens, representing110 species, besides 7 distinct varieties, of which more thanhalf are well preserved in spirit and the remainder are dry. Thedistricts searched consist of:— 1. Port Jackson, N.S.Wales; 2.Several points on the north-east coast of Queensland ; 3. Variousislands and spots in Torres Straits ; 4. The Arafura Sea, betweenCape York and Port Darwin; 5. Port Darwin, N.W. Australia.The depths range from between tide-mai'ks to 36 fms. (Arafura Sea),but most dredgings did not exceed 20 fms. in depth.It is perhaps not surprising, after what has been stated as to theprevious work which has been done among the Australian Sponges,to find that a large proportion (42 out of 110, or 38 per cent.) ofthe species are certainly new to science, and that a considerablenumber more may possibly prove to be so, having been assigned onlydoubtfully to described species. However, the distribution of thelittoral species (when these are properly defined and limited) ofSponges appears usually to be but moderately wide, and perhapsless so than the shallow-water Alcyonaria ; both this and anotherfact must be adduced to account for this large number of new species,viz. that the sponge-faunas of the neighbouring and moderatelydistant seas are even less known than that of Australia itself ; thiswill be seen clearly from a statement of what has been done toelucidate the fauna of the Indian Ocean which I have made underthe heading Geographical Distribution. I have in this dearth ofinformation taken pains to describe every form which warranteddescription. I have been careful not to assign a new name wherethe sponge might possibly have been already described, in order notto run the risk of adding to the overburdened synonymy, but havegenerally given a full description in such cases, so that no doubtmight remain as to the characters of that species, at any rate, withwhich I have had to deal.Taxonomy of the Collection.—Of the 1 10 species obtained, 20 (ormore than one sixth) are Ceratosa, a number which is illustrative ofthe largely tropical character of the localities from which they aredrawn ; the Dysideidsc include two new species and a most interestingvariety of a most important form, Psammopemma densum,Marshall, whose nature receives hereby confirmation and elucidation; the number of new Ceratosa (4) is not great, as most of thespecies seem to have a wide range.The Silicea, as usual, far outnumber the other groups ; the