OCR Text |
Show 1876.] DR. J. s. B O W E R B A N K O N T H E SPONGIAD^E. 769 compressed and very solid in its structure. The hispidity of the surfaces is produced by the projection of the secondary lines of the skeleton, which are uniform in length on both surfaces of the sponge ; but they are more abundantly produced on the surface presented to the eye in the figure than on the opposite one ; and they always terminate in plumous expansions. The primary lines of the skeleton are projected in slightly meandering lines, but always in the same plane ; and none of them exceeds about a quarter of an inch in diameter. The oscula are abundantly dispersed on the primary lines of the skeleton ; they are very minute, and are scarcely perceptible without the aid of a lens of about 2 inches focus. The dermal membrane is closely adherent to the spiculo-fibrous structures of the skeleton; and it can be seen distinctly only when small portions of the sponge are mounted in Canada balsam, in the form of thin expansions within the areas of the rete of skeleton-fibres. There is but one form of spiculum, the subfusiformi-acerate one ; their average proportions are T^-T inch in length, and TArs* "ich in diameter. The general aspect of this sponge is very remarkable : all the secondary plumous fibres projected from either surface rise to nearly the same height, rarely exceeding that of about a quarter of an inch ; and all of them assume the same plumous expansion of their apices. The skeleton-structure is purely that of a Desmacidon; but its peculiar mode of development differs widely from every other species of the genus with which I am acquainted. CHALINA VERTICILLATA, sp. nov. (Plate LXXIX.) Sponge pedicellate ; pedicle long, smooth ; proximal portion without sponge-plates ; distal portion sustaining a succession of numerous thin perfoliate more or less circular cup-shaped plates of sponge, decreasing in size to the apex. Surface-upper and under surfaces of the plates rugose, margins entire. Oscula simple, dispersed, numerous on the under surfaces of the plates. Pores inconspicuous. Dermis reticular, rete irregular ; dermal membrane sparingly spiculous ; spicula depresso-spinulate, same size and form as those of the skeleton, dispersed. Skeleton symmetrical, radiating irregularly from the centres of the plates ; primary and secondary lines slender and delicate, not very numerously spiculous; spicula depresso-spinulate, rather variable in length and diameter. Interstitial membranes sparingly spiculous ; spicula same as those of the skeleton. Colour, in the dried state, nut-brown. Hab. Fremantle, Australia (Geo. Clifton, Esq.). Examined in the dried state. The height of this sponge is 13 inches, and its greatest breadth 3 inches. At 5 inches from the basal attachment the pedicle divides and becomes two branches ; at the part from which the lowest of the plates of the sponge is projected, and thence to the apex, they are produced in a rather irregnlar series. The form of this sponge is remarkable and unusual ; but the species in course of description is not the only one in which we find it. The whole of such sponges |