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

—SPONGIIDA. 625TETBACTINELLIDA.As usual with shallow dredgings like those of he ' Alert,' thefamily Choristidte is alone represented. The proportion of speciesto the rest of the collection is about the same as in the Australiancollection ; but we miss the genera Geodia and Placospongla, whichmight have been expected to occur here. The remarkable group withdiscoid dermal plates which stands between Geodia and SteUetta isrepresented by a new species.CHOEISTID^.4U. Tetilla dactyloidea.Tethya dactyloidea, Carta-, Ann. 4" Ma(/. N. H. 1869, iii. p. 15, figs,1-5 ; 1872, ix. p. 82, pi. 10. figs. 1-5.A somewhat imperfect specimen, having, however, probably hadsomewhat the form of Tlienea tvalliclii, "Wright, when perfect^t. c.not produced upwards into the long cylinder figured by Mr. Carter,but depressed and agariciform. Its diameter is much greaterthan that of Carter's specimen, viz. 40 millim. (1| inch); its presentheight is 25 millim. (1 inch). The spicules agree closely withMr. Carter's descriptions and figures, with the exception that theforked anchor does not exhibit a constant inequality in the lengthof the arms.Hah. Glorioso Islands, low water.Distribution.S.E. coast of Arabia (^Carter).ERYLUS, Gray.SteUetta, pars, Schmidt, Spony. Aclr. Meer., Spong. Kilst. Alt/., Spong.Atl. Get. ; Carter, Ann. ^ Mag. N. H. 1880, v. p. 135.Erylus and Triate, Gray, P. Z. 8. 1867, p. 549.Discifera, of subsection Pycnodermata of group Stellettina, Carter,Ann. ^ Mag. N. H. 1883, xi. p. 348.I have already indicated (Part I. pp. 471, 472) that the speciescalled by Schmidt SteUetta, but provided with disks composed ofmodified trichites, should be definitely separated from that genus.I adopt for this distinct group the generic term which Dr. Grayassigned to S. mamillaris, Schmidt. It may be characterized as :Comprising Choristid Tetractinellida with the surface covered by alayer of detached discoid trichite globates, and having besides a zonespiculeand small stellates with slender and few rays. Formlobate. Vents single or multiple.It differs from Geodia in the discoid form of the trichite massesand their independence of each other (in Geodia they are united byligaments). It includes the described species SteUetta euastrion, S.mamiUaris, and S. discophora, Schmidt, and S. eiiastrum, Carter.SteUetta (jeodina and S. intermedia, Schmidt, should be referred toQeodia.2s