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Show 288 DR. J. S. BOWERBANK ON THE SPONGIADcE. [Apr. 6, description of both of these organs require the application of a power of at least 400 linear to render them distinctly to the eye. Their minuteness is such that they do not exceed in length the diameter of a skeleton-spiculum, TAro iuch. The skeleton-rete is strongly developed, and the spicula are comparatively short and very stout. The nearest alliance to this sponge among our British species is Halichondria forcipis. Its general habit, the forms and modes of disposition of the spicula of the dermis, and the form and proportions of the skeleton-spicula exhibit close resemblances ; but in other important characters the two species are essentially different. HALICHONDRIA FRONDIFERA, Bowerbank. Sponge branching from the base numerously; branches rather compressed, frequently dividing, distal terminations spinoid. Surface minutely rugose. Oscula simple, minute, dispersed. Pores inconspicuous. Dermal membrane abundantly spiculous; tension-spicula acuate, rather long and slender, dispersed; retentive spicula bidentate equianchorate, very minute and few in number. Skeleton-rete multispiculous, compact, rather close and strong, areas small; spicula acuate, rather stout and short. Internal defensive spicula attenuato-acuate, entirely spined, short and stout, uniform in size, rather numerous. Colour, in the dried state, dull grey. Hab. Straits of Malacca and Gaspar Straits (Commodore Parish, R.N.). Examined in the dried state. I am indebted to m y friend Commodore Parish for this remarkable sponge; he obtained it with many others from the Straits of Malacca. It is attached to the shell of a small Spondylus, nearly the whole of the valve of which is covered by the thin basal portion of the sponge, from which numerous slender compressed branches are given off, some of them nearly two inches in length; each of these branches resembles in form a stag's horn, but with many more divisions than would be possessed by the horn. The oscula are simple and minute, a few only near the distal terminations of the branches being visible with the aid of a lens of two inches focus. The tension-spicula of the dermal membrane are exceedingly numerous, so much so as almost to present a felted appearance ; they are quite as long as those of the skeleton, but not more than half their diameter. The bidentate equianchorate retentive spicula are very minute and slender, and very few in number: I could not detect them in situ; but amidst the spicula prepared by the action of nitric acid I found them on some of the fragments of the dermal membrane and a very few among the other spicula; one of the largest of them measured -g-g-Vo" iQcn ^a lerjgth. They require a power of about 400 linear to render them distinctly to the eye. The attenuato- acuate, entirely spined, internal defensive spicula are uniform in size and rather numerous; they are based on the skeleton-rete and |