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Show 1868.] DR. J. S. BOWERBANK ON SPONGES. 131 having previously disposed of the latter as Donatia aurantium, page 541, in accordance with the views of Nardo. My two species, Mon. Brit. Spon. vol. ii. pp. 87 &89, are converted into Collingsias ; and Tethea muricata, of which he knows nothing, but the form of one sort of retentive spiculum, he transforms into Thenea muricata. Tethea robusta and T. ingalli, of which he knows nothing but the fio-ures of a spiculum of each represented by figures 164 & 165, plate 6. vol. i. Mon. Brit. Spon., he at once consigns to the rejected genus Cy-donium, Fleming, resuscitated by Dr. Gray to be thus filled by his fertile imagination with species. Dr. Gray thus disperses the species of one of the most striking genera with which we are acquainted among sponges-so much so that the student who has become acquainted with one species can scarcely fail at the first glance to assign any others he may acquire to their proper genus in existing arrangements. The author has arranged the Geodiadce in his Order VI. Sphcerospongia, page 547. In the definition of this order he has two names for the same organ in one sentence. In place of ovarium he has first ovisac-cells and then ova-cells ; and in his description of the family Geodiadce, immediately following, there is a third variation, ovisacs. Instead of placing the type genus of the family, Geodia, Lamarck, first, he gives that position to m y genus Pachymatisma, decidedly an aberrant one, and places Geodia second. He then separates all the species of Geodia described by Prof. O. Schmidt and by me, and places them under the very doubtful genus Cydonium, Fleming, page 548, thus-"2. Cydonium muelleri \_mulleri\ Fleming, B. A. 516," in which Dr. Fleming describes his genus as having " polypi with a central opening and an orifice at the base of each of the eight pinnated tentacula,"-showing either that he had greatly mistaken the nature of Geodia zetlandica, Johnston, or that he had described the orange-coloured variety of Alcyonium digitatum, Johnston's ' British Zoophytes,' 2nd ed. vol. i. p. 174. The latter appears to be the most probable. Dr. Gray then, to increase the confusion, adds to the genus Cydonium Tethea ingalli and T. robusta, from the figures of spicula only from each quoted by m e in ** Monograph of British Spongiadse,' vol. i. pl. 6. figs. 164 & 165, leaving Lamarck's genus Geodia to be represented by the type species, G. gibberosa, and one other, G. caribea, Duchass. et Michel. I have had the opportunity of carefully examining Lamarck's type specimen in the Jardin des Plantes, Paris, and am well acquainted with its organic structure ; and I will veuture to say that no practical naturalist who has had the like advantage and was acquainted with the other well-known species of Geodia would for one moment dream of separating them from Lamarck's genus. To complete the confusion of ideas, we then have a specimen of Pachymatisma, P. listeri, on the faith of the form of one spiculum, figs. 50 & 51, pl. 2, Mon. Brit. Spong., transformed into a new genus, Triate, page 549 of the author's paper, and, by the same uncertain means, identified with Prof. O. Schmidt's Stelletta |