Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/350

242 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. living condition this Sponge would probably exhibit a smooth membranous surface; but in its present state we have large open areas exhibited in lieu of the smooth dermal membrane. These areas are in fact the distal ends of the intermarginal cavities, and are usually much larger than the interstitial spaces immediately beneath them. In the specimen under consideration, as in similarly organized recent Sponges, the proximal terminations of the intermarginal cavities communicate immediately with the distal ones of the interstitial spaces, and then, uniting, increase in their size as they progress towards the inner parietes of the great cloacal cavity of the Sponge, into which they finally discharge their streams through the oscula. In this organization they closely resemble the structures in the recent genera Grantia and Verongia, and many of the fistular keratose Sponges of the West-Indian seas.

I have not detected any connecting spicula; and I have assigned the angulated sexradiate ones to the interstitial cavities on the faith of some very dilapidated remains of them, deeply immersed in the tissues, and rendered visible only by the penetrating power of the Lieberkuhn.

The nearest relations to this tribe of Sponges among the fossil ones are decidedly the siliceo-fibrous Sponges of the Flamborough Chalk; and below that formation I am not aware of any such Sponges having been found. The matrix of the Australian fossil also possesses much of the character of Chalk; it dissolves completely in dilute hydrochloric acid, and leaves only a small quantity of sandy residuum.

I may also observe that the similarity of form and structure between the Australian and the English Chalk Sponges in this case is by no means a new fact, as there are abundant instances of similar close alliances existing among the recent Australian Sponges and those of the Chalk-formation of England; and among the most prominent are the existing representatives of Choanites and Ventriculites. — J. S. B.]

2. Cristellaria cultrata, Montfort, var. radiata, Moore.

This shell, of which I have discovered but one example, possesses the central disk of G. cultrata, from which the ribs on the surface proceed; and although the keel is less produced, there appears no doubt it must be referred to this species. From the more radiating character of the costae, I propose for the variety the name of G. radiata. It is from Wollumbilla.

3. Cristellaria acutauricularis, Ficht. & Moll, var. longicostata, Moore.

Shell oblong, moderately biconvex, later chambers passing beyond helicoid portion; surface with ribs which are longitudinally costated.

The typical European forms of C. acutauricularis, which are found also with this shell, possess smooth surfaces, and are without the longitudinal costae, — the difference being so marked as to justify