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Show 1875.] DR. J. S. BOWERBANK ON THE SPONGIADcE. 291 linear to define their forms distinctly; proportionately they were rather stoutly and strongly formed. The structural peculiarities of the skeleton form a very striking specific character in this species. The rete is strongly and compactly formed, and the number of spicula in any part of it is far greater than can be counted. The areas are unsymmetrical and rather variable; and the interstitial membranes filling them are frequently abundantly supplied with the same description of spicula as those of the dermal one. HALICHONDRIA COMPRESSA, Bowerbank. Sponge branching irregularly and abruptly ; branches compressed. Surface more or less rugose or spinous. Oscula simple, dispersed. Pores inconspicuous. Dermal membrane spiculous ; tension-spicula subclavate acuate, variable in form, dispersed or more or less fasciculated ; retentive spicula bidentate, rarely tridentate equianchorate, comparatively large and very stout, rather few in number ; and the same form minute and slender, numerous. Skeleton-rete multi-spiculous, very irregular; areas large and variable in form ; spicula acuate, rather short and stout. Interstitial membranes sparingly spiculous ; spicula same as those of the dermis. Colour, in the dried state, dark green. Hab. Straits of Malacca (Commodore Parish, B.N.). Examined in the dried state. I received this remarkable sponge with others from m y friend Commodore Parish, who obtained it from the Straits of Malacca. It is rather less than 2 inches in height, and less than an inch wide at its greatest expansion. The external form is remarkably singular. It rises from a very small base, and immediately branches abruptly in every direction and at every possible angle. The branches are nearly all of the same size, and are all more or less compressed, and their surfaces rough and irregular. The dermal membrane is comparatively stout, and in most parts it is abundantly spiculous. The tension-spicula are occasionally sub-fasciculated, or so numerous as almost to appear felted together ; while in others they are dispersed singly, and rather sparingly distributed, crossing each other at various angles. These spicula are subject to considerable variation in form : all of them are more or less subclavate at the base, but their shafts exhibit the greatest amount of variation ; some are quite attenuato-acuate, while others terminate so obtusely as to closely approach the cylindrical form ; and gradational forms- between the two extremes are of frequent occurrence. The bidentate equianchorate retentive spicula also exhibit very remarkable characters. There are two very distinct sorts of them-one comparatively large and of very robust structure, the other very minutely slender aud delicate; both have their shafts semicircular. The larger ones average -6J0 inch in length, with a diameter of shaft of ¥ - ^ inch; the smaller series never appear to exceed T ^ inch in length, and the shaft of one of the |
