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Show 508 DR. BOWERBANK ON SILICEO-FIBROUS SPONGES. [June 15, any remarkable characters. The fibres are usually quite smooth; occasionally, however, there are small and very immature rectangulated sexradiate defensive organs; but I did not see a single well-produced one. There were a few small portions of the dermal membrane in a good state of preservation, upon which there was a rather thick layer of sarcode; but I could not detect in it any thing in the shape of spicula. The specimen from which the above description has been made was in the possession of m y late friend Mr. Henry Deane, who kindly obliged me with the use of it for description ; and his son, Mr. James Deane, has kindly given me the specimen. FARREA SPINOSISSIMA, Bowerbank. (Plate LVII. figs. 3 & 4.) Sponge cup-shaped? Dermis, oscula, and pores unknown. Skeleton rectangulated, composed of three or four layers ; fibres of the external ones of rather greater diameter than those intervening, more regularly disposed; areas variable in size and form, abundantly armed with very long, slender, defensive prickles, projected in various directions, more or less incipiently spinous, spines acutely conical- and also sparingly with rather small rectangulated sexradiate internal defensive organs. Skeleton-fibre rather slender, usually smooth, occasionally furnished with a few acutely conical spines; central canals variable iu size, usually slender, occasionally obsolete. Sarcode, in the dried state, dark amber-brown. Colour, in the dried state, dark amber-brown. Hab. Unknown. Examined in the skeleton-state. I am indebted to m y late friend Mr. Henry Deane for the only specimen of this species with which I am acquainted. It is a plate of skeleton-tissue 8 lines in diameter. It is curved to such an extent as would seem to indicate that it had formed part of a cup-shaped sponge two or three inches in diameter. In some parts of the structure there are as many as four layers of the skeleton-tissue; but the number most frequently seen is three. The prominent and most distinctive character is the long slender prickles projecting from the skeleton-fibres at right angles to their long axis ; sometimes one only is thus produced, but more frequently two in opposite directions, or three are thus projected at about equal distances from a line encircling a fibre. They are always very slender ; but they differ in length to a considerable extent: in some cases their length is about equal to the diameter of the fibre on which they are based; but they are frequently three or four times that length. I could not detect the slightest indication of dermal or iuterstitial membranes with a power of 80 linear; nearly the whole of the skelelon-fibres were more or less covered by a thin coat of dark amber-coloured sarcode; and the long defensive prickles were much more thickly coated with the sarcode than the skeleton-fibres; and this coating of the prickles was mostly thin at their proximal ends, and gradually increased in its thickness to their distal extremities, frequently becoming slightly clavate. |