their lower extremity. It is possible the Paramoudra, having a tube with two apertures, may have possessed a character intermediate between a gigantic spunge and an ascidia. I have broken very many of these fossils in search of internal organization, and in one case only found the appearance represented in Pl. 24. No. 7, and there magnified beyond its natural size. It presents a small cluster of hexagonal cells about of an inch in diameter. The substance of the septa dividing the cells does not exceed in thickness that of the finest paper, and appears to be silex much iron-shot; the cells are filled with silex of the same colour with the mass that envelopes them, and display no traces of radii or fibres traversing their interior. This small cluster of cells was decidedly inclosed in the body, and within the crust of a Paramoudra, extending inwards, not an inch from the epidermis. As this is the only specimen in which I have seen or heard of such traces, I think it more probable that they are a fragment of some extraneous body, that was accidentally attached to, and at length inclosed within the substance of the Paramoudra, than that the traces of an organization so distinct and decided, if it had ever existed generally, should have been so totally destroyed in every other specimen that has been examined, as to leave only the outward form to guide us in our conjectures as to the character and habits of the original animal.
The mineral history of the Paramoudra seems intimately connected with that of many other spungiform bodies which we find in chalk flints. In all these cases the organic bodies thus preserved, appear to have been lodged in the matter of the rock, while it was in the state of a compound, unconsolidated, pulpy fluid; and before that separation of its siliceous from its calcareous ingredients, which has given origin to the flinty nodules in chalk, and to beds and
