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Show 1875.] ON ALCYONCELLUM SPECIOSUM ETC. 607 lacerati; in valvula sinistra dens lateralis inter duos valvulce dextrce insertus. Long. 1 poll., lat. I1 poll. Hab. Birmah, vel Pegu. Mus. Hanley. The beaks are eroded in our only specimen of a shell (Conch. Indica, pl. 155. f. 3), which reminds us somewhat in structure of the Unio tavoyensis of Gould. When held before a light the valves appear of a yellowish green, richly embossed with zigzag ridges of a darker or bluer verdure. The hinge is nearly the same as in U.favi-dens of Benson, the central teeth being short and very complicated. 5. Further Observations on Alcyoncellum speciosum, Quoy et Gaimard, and Hyalonema mirabile, Gray. By J. S. BOWERBANK, LL.D., F.R.S., F.Z.S., &c " [Received September 24, 1875.] On Wednesday the 8th September, 1875, I received ajar of specimens from Commodore Parish, of Hong-Kong, which he stated he obtained from the ' Challenger' when there. The specimens were preserved in spirit in the condition in which they were taken from the sea. They consisted of two specimens oi Alcyoncellum speciosum with their dermal membrane and sarcodous substance in a fine state of preservation, one fine specimen of Hyalonema mirabile with the basal sponge in fine condition and with its dermal membrane in perfect preservation, and a fine head of a recent pentacrinite with about three inches of its stem with side arms in a good state of preservation. These specimens, especially those of Alcyoncellum speciosum and Hyalonema mirabile, are exceedingly interesting, as their perfect state of preservation enables us to complete our knowledge of their anatomical peculiarities to a much greater extent than those, in a more or less imperfect condition, with which we have hitherto been acquainted. On mounting in Canada balsam small portions of the two specimens of Alcyoncellum speciosum, I found in a fragment from near the distal end of one of them the beautiful dermal expansile system of reticulated structure, composed of slender rectangulate sexradiate spicula, the distal ray of each terminated by a spinulo-quadrifurcate sexradiate stellate spiculum, which is so beautifully exhibited in the highly interesting skeleton of the specimen from a sponge of the same species presented to m e by m y friend Dr. Millar, and described by m e in Part IV. of m y " Monograph of the Siliceo-fibrous Sponges," in the Society's 'Proceedings' for 1875. The complete envelopment of these beautiful tissues by the dermal sarcode of the specimens in a natural state renders the identification of these delicate defensive organs by no means an easy task ; and in truth, without the indications of their forms and proportions afforded by Dr. Millar's specimens, we could scarcely have hoped to detect them in situ amidst the dense amber-coloured sarcode in PROC. ZOOL. Soc-1875, No. XXXIX. 39 |