| OCR Text |
Show 294 DR. J. S. BOWERBANK ON THE SPONGIADcE. [Apr. 6, mary lines multispiculous ; secondary lines very irregular, mostly unispiculous, occasionally bi- or trispiculous ; spicula acuate, stout, and rather short. Interstitial membranes sparingly spiculous; spicula same as those of the dermis. Colour, in the dried state, pale ochreous yellow. Hab. Straits of Malacca (Commodore Parish). Examined in the dried state. The external characters of this species are by no means prepossessing. It is a rough and very uneven mass, 2 inches in length and about 1 inch in greatest diameter, full of ridges and depressions. Sections cut at right angles to the surface do not readily illustrate the characteristic structure of Isodictya, in consequence of the coarse and irregular nature of the skeleton; but on a more careful examination the presence of the stout continuous primary lines of the skeleton unmistakably lead us to a correct determination of the genus. The dermal membrane is very characteristic of the species. It is abundantly supplied with long, slender, acerate tension-spicula, irregularly distributed and crossing each other in every direction, These spicula are quite as long, and frequently longer, than those of the skeleton, while their diameter varies from half to one third of those of the last-named organs. The skeleton-structure is very open and irregular, and the spicula in the primary fibres are very numerous ; they are acuate and comparatively stout and short. The secondary lines are very irregularly distributed and rather numerous; so that when a section of the sponge is hastily examined, it is very liable to be mistaken for that of a Halichondria. I received this species from my friend Commodore Parish, who obtained it from the Straits of Malacca. ISODICTYA VIRGATA, Bowerbank. Sponge virgultose, more or less fistulous. Surface smooth. Oscula simple, dispersed, rather large. Pores • inconspicuous. Dermal membrane spiculous ; spicula acerate, same size and form as those of the skeleton, reticulated ; rete rarely more than unispiculous or bi-spiculous, areas irregular in form ; retentive spicula bihamate, simple, and contort, rather numerous, minute. Skeleton diffuse and irregular ; primary lines multispiculous, spaces between them varying from one to two spicula in width, rarely wider; secondary lines bi-or trispiculous, irregular. Interstitial membranes furnished abundantly with minute simple and contort bihamate retentive spicula, same as those of the dermis. Colour, in the dried state, pale ochreous yellow. Hab. Straits of Malacca (Commodore Parish). Examined in the dried state. This sponge consists of two short branches based on a small fragment of stone or coral; the tallest of the two does not exceed 2 inches in height, and about 2 lines in diameter; for a portion of its length there is a central fistulous cavity, but it does not appear at the |
