OCR Text |
Show 328 DR. .I.S. B O W E R B A N K O N T H E SPONGIAD/E. [Mar. 18, radial structure prevails in patches only, and the connecting-spicuia are comparatively rare, and frequently in an imperfectly developed condition. The skeleton is abundantly spiculous; the two forms, the acerate and acuate, are indiscriminately mixed in its structure ; but the former prevail to a much greater extent than the latter ones. The short stout tension-spicula of the interstitial structures are unusually large and strong; they are very numerous, and are irregularly dispersed on all parts of the membranes. The two forms of stellate retentive spicula are very abundant, and are irregularly dispersed over all parts of the membranes. The larger of the two, the attenuato-stellate ones, are very numerous; they vary to some extent in size and in the number of their radii; the one represented by fig. 11, Plate XXXI., is a very fully developed specimen. The minute sphero-stellate spicula also vary somewhat in their size and form, the radii in some being much more conical than in others; and they are very much more numerous than those of the larger form. The sponge is evidently an adult specimen, as nearly all the # ovaries are in the solid or exhausted condition, and very few immature ones were observed on the more deeply seated parts of the interstitial membranes. GEODIA PARASITICA, Bowerbank. (Plate XXXI.) Sponge sessile, coating ; surface even or slightly nodose, smooth. Dermal membrane translucent, furnished abundantly with minute sphero-stellate spicula. Connecting-spicuia attenuato-subpateuto-ternate, few in number. Oscula simple, dispersed (?), few in number. Pores congregated, porous areas abundantly furnished with small sphero-stellate retentive and defensive spicula; radii numerous, short, acutely conical. Skeleton spicula fusiformi-acerate, large and stout, numerous. Interstitial membranes-tension-spicula fusiformi- acerate, small and slender ; retentive spicula small, sphero-stellate, the same as those of dermal membrane, rather numerous. Ovaria globose, rather depressed. Colour, in the dried state, light cream-yellow. Hab. Unknown (Mr. Thos. Ingall). Examined in the dried state. I am indebted to my late friend Mr. Ingall for my knowledge of this species. It was originally, I believe, parasitical on the base of a coral. In its present condition it consists of fourteen fragments, the largest of which slightly exceeds half an inch in diameter ; when entire it probably covered about 11 square inch ; and the thickness does not appear to have exceeded \ of an inch in any part. The surface has evidently been uneven, with one or more nodular elevations. The surface is smooth, and there does not appear to have been any large or small spicula projected beyond it. A few oscula were apparent on the fragments, two of which were nearly one tenth of an inch in diameter ; and on one fragment there was apparently the remains of a portion of a sunken area, which may |