18/6.] DR. J. S. BOWERBANK ON THE 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 ter- 

 minate 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 dia- 

 meter. 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 fy inch in length, and -j hVs~ mcn U1 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 Desmaeidon; 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 with- 

 out 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 spicu- 

 lous ; 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 mem- 

 branes 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 irregular 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 



