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

—SPONOIIDA.Of the two species assigned by Mr. Carter (I. c.) to the genus,S. simplex, recorded from Freemantle, Australia, and Hayti, is themost closely allied to the present, but differs from it in the possessionof the bacillar tuberculate flesh-spicule. Mr. Carter, however,described in the same paper as that in which he foundedSteUeUinopsis (torn. cit. p. 344), a species which even more nearlyapproaches the present : this is AmorpJiina stellifera from SouthAustralia, which differs from the present form only in its amorphous,non-pedicellate growth and the proportions of its spicules,which I now give, reduced to metric measurements :1. Acerate, -7 by '017 millim.2. Stellate (stated to have no central inflation ; that in S. carteriis hardly worth the name), -017 millira. in diameter.Thus the acerate is one fourth and the stellate two thirds smallerthan in our species, and hence the two species are, in my view, sufficientlydistinct. Amorphina stdlifera should, however, stand asSteUeUinopsis stellifera.TETHYOPSIS.Steivart, Quart. Journ. 3Iicr. Sci. n. s. x. (1870) p. 281 (nee Zittel,Abh. buyer. Ak. xiii., ii. (1879) p. 9).To this remarkable genus I propose to assign a species whichhas, as described recent allies, the species T. columnifera, from the PhilippineIslands, on which the genus was based, and Tribrachion (um)schmidti, from the Gulf of Mexico. Like the latter, the presentform exhibits a singular divergence from the more normal Tetractinellidtypes, in that its chief spicule has lost one of its arms, andis only triactiuellid. The genus appears to be allied to JStelletta,the peculiar development of its large tetractinellid spicule beingapparently caused by the erect growth aiid non-corticate characterof the sponge.(Plate XL. fig. H ;105. Tethyopsis dissimilis.Plate XLIII. figs. l~l"""".)Sponge elongated, slender, cylindrical or suboblong, taperingto the free extremity, which is pointed ; attached by a narrow basewhich throws out a thin horizontal expansion outside the spongeitself. Flexible ; surface formed by a thin and delicate dermal membraneof a dark grey colour in spirit. Yent ? Pores •04--08 indiameter, crowded in the interfascicular spaces of the dermis.Skeleton formed by a number of narrow Ijands of aggregated spiculeshafts(spicule Xo. 1) running longitudinally down the interior of thesponge; the bands are united laterally (see fig. V") by means of thearms of the triradiate spicule, are clothed with the soft tissues,and serve to break up the space within the sponge into 8 or 9elongated cavities running from the base towards the apex of thesponge, viz. (1) anterior, (2) posterior, (i3 and 4) lateral, (5 and 6)antero-lateral, (7 and 8) postero-lateral, and in one case (9) axial (seefigs. I and I'). Subdermal skeleton formed by similar longitudinal