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Show 1869.] DR. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 89 while others appear to have no connexion with the tissues beneath them. DACTYLOCALYX PRATTII, Bowerbank. Sponge irregularly cup-shaped, pedicelled; surface even, slightly undulating. Oscula simple, small, dispersed, numerous. Pores congregated in areas formed by the distal terminations of the expando- ternate connecting spicula, numerous and large. Expansile dermal system-dermal membrane pellucid, furnished abundantly with minute entirely spined fusiformi-cylindrical spicula, short, frequently semilunate or angulated, irregularly dispersed. Connecting spicula irregularly furcated patento-ternate; radii slightly depressed, apices thin and expanded; ternate heads combining to form a dermal network. Enveloping membrane of the rigid skeleton abounding with the same minute spicula as those of the dermal membrane, and also with numerous separate flat fasciculi of long and slender acerate tension-spicula. Skeleton-rete compact; fibres smooth, or irregularly and slightly spinous ; free terminations of fibres ramose, or abundantly tuberculated. Interstitial spicula acerate, long, slender, and frequently flexuous, mostly disposed iu lines at right angles to the dermal surface. Interstitial membranes pellucid, furnished with the same form of retentive spicula as the dermal membrane. Colour in the dried state, light brown. Hab. East-Indies (S. P. Pratt, Esq.) ; off the island of Formosa (Mr. Swinhoe). Examined in the dried state. I am indebted to m y late friend Mr. S. P. Pratt for the very interesting specimen under consideration. He stated that he was not quite certain of its locality, but he believed he had received it from his son, who was then in India, along with many other interesting marine specimens. The form of the sponge is that of an irregularly shaped cup, the rim of which is nearly an oblong, 4 | inches long and 3^ inches wide ; and at one corner there is a depression of the margin, so as to form a lip to the cup of rather more than an inch in depth. The height of the cup in its present state is 4 inches. It has been broken away from its natural base ; but, from the indications remaining, it is probable that it was elevated on a short pedestal. The margin of the cup is unequal in its thickness, varying from half an inch to a thin sharp edge. The specimen was evidently in a living state when taken from the sea, and it is still in an excellent state of preservation. The oscula are simple orifices, without any especial defensive organs ; they have the usual contractile membrane to open and close them in accordance with the necessities of the amimal. The greater portion of them were closed, while others were more or less open. Through one in the latter condition, in a slice from the surface mounted in Canada balsam, the surface of the rigid skeleton was seen, covered by the enveloping membrane, which was closely adhe- |