Species.

154. S. botryoides....... With oblong, ovate lobules, apices

hollow and open.

155.

radiciformis....With

branches, compressed at the

apex.

prolifera.........Palmated, with frequent divisions, and distinct finger-formed pro

161.

nally muricated.

....Amorphous and subramose.

...Confluent, with ramose fasciculi;

floribunda

having a chaffy flosculent down, and being obtuse and thicker at the apex.

baccillaris ...... Erect, caulescent; with porous branches, applied to each other.

The existence of fossil sponge in the transition or in the mountain limestone has not been ascertained, or in the different beds of the lias formation; but the tenuity, in general, of its substance, and the nature of the matrices in which it has been sought, may perhaps occasion its concealment. Of its presence in the several oolitic beds, I have not been able to acquire any satisfactory information, except that in the Portland freestone I have seen semisphæroidal masses, about eighteen inches in diameter, divided into flattish, foliaceous, laciniated, erect lobes, and which appear to possess a spongeous structure. Specimens are sometimes found in the green sand formation, but not so frequently as may have been expected: the specimens which are most frequently found, are, I suspect, those which are adherent to the accompanying fossil shells.

The richest collection which is known of these fossils is, I believe, that of the gravel pits of the iron sand at Farringdon, where they are found mingled with the fossils of some of the early formations. Some of these specimens are of con

siderable size, and are in such excellent preservation as to allow, at least, of their arrangement under the more comprehensive divisions of the genus. Among the specimens are round and cavernous, resembling sp. globosa; pediculated, sub-pediculated, lobated and flabelliform, ramose, foliaceous, cyathiform, funnel and ficiform. In most of the specimens the structure and form of the substance are so obvious, as to raise the hope that the determining of their specific characters, and of their consequent arrangement by some zealous investigator of these interesting relics, may be expected.

Fossil remains of this substance are frequently found in the chalk, and most numerously perhaps in the lower series of this formation; but from the delicate texture of the membrane of the sponge, and from its cavities being filled by the chalk itself, there are no known means by which the fossil can be extricated from its matrix. Indeed, it frequently happens that these substances, agreeing as to colour with the chalk, would exist there undetected, but by the greater degree of hardness which it possesses, and by the asperities which it presents at the surface. They are sometimes pointed out by the strong tint which they derive from having sustained a ferruginous impregnation; and in these instances, although a sufficient separation from the surrounding chalk to allow the developement of the form cannot be obtained, yet, by their being carefully rubbed down to a smooth surface, something of this may be discovered, with, generally, a tolerable display of the internal structure.

The nodules of chalk flint frequently contain the silicified remains of sponge, and in a state which will allow

H.

their form and structure to be much more easily traced than in the chalk itself. The most common forms in which these occur are oblong or nearly globular: and they are either imbedded in the chalk, or scattered on its surface, or in the neighbouring declivities. These may be frequently found on the Sussex Downs, the Gogmagog Hills of Cambridgeshire, and, indeed, on or about most of the chalk hills. These nodules appear to have been formed round fragments of sponge of different forms and structure, and to be more or less filled, according to the degree of decomposition and subsequent removal which the included substance had sustained after its inclusion. In some specimens, particularly among those of Wiltshire, which have been collected by the liberal encouragement of Miss Benett, a tuberous or ramified body, and, in some instances, two such bodies, are extended across the cavity of the flint, and covered over with a fine white powder of chalk and silex blended. These bodies appear to be casts in the cavities of sponge, the substance of which has passed away. In others the substance which had been included appears to have been broken down and removed, and its place occupied by chalk which has intruded in a pulverulent state; whilst in others the cavity alone remains. Oblong nodules, found on Stokenchurch Hill, and for some distance on the Oxfordshire side, very frequently exhibit specimens, which, on being broken, display the structure of the Zoophyte in great distinctness. In the chalk marl at the foot of the cliff at Beechey Head, are botryoidal and lamelliform masses, which, not only from their external forms, but the appearances yielded on their fracture, lead us to the recollection of the masses of fossil sponge at Farringdon, and which, in all probability, have been yielded by the chalk marl.

Fossil sponge of a very fine texture, and in a pulvinated form, is sometimes found investing the shells accumulated in the cliffs at Walton and Harwich.

A flint stone, found on the shore at Dawlish in Devonshire, bears decided marks of having derived its form from the siliceous impregnation of sp. mammillaris.

Several fossils of the tribe of Zoophytes having been noticed in a former work, which, although not possessing the decided characters of the genus, were still, with expressed doubt, placed among the Alcyonia; an attempt at a better classification of some of these bodies is here attempted.

The first of these, are those bodies which are distinguishable by bundles of tubuli passing through a spongeous substance, and which may be thus characterised.

Siphonia. A fossil animal, with a polymorphous body, supported by a stem proceeding from a fusiform or ramose root-like pedicle; the original substance spongeous, and pierced by a bundle of tubes derived from the pedicle, passing through the stem, then ramifying and terminating on the surface of the body.

The various spongeoid fossils, bearing the forms of cups, funnels, fruits, &c. described by M. Guettard, as obtained from Verest, near Tours and Saumur, and at Montrichard, in Touraine, and by the Rev. J. Townsend, as found in the green sand of the Vale of Pewsey*, as well as those which are figured, Pl. ix. fig. 1, 4, 5, 7, 11, 12, 13; Pl. x. fig. 6 and 13, of the second volume of Organic Remains, &c. are of the same genus.

Since the publication of the last mentioned work, Mr. Webster made the discovery of those interesting fossils in the Isle of Wight, which from their long seeming stalks, and from their tulip-formed superior terminations, obtained

* The Character of Moses, &c. Pl. 1, fig. 1. Pl. 2, fig. 1, 2, 3. Pl. 3, fig. 1, 2, 3.

the name of tulip alcyonia*. These fossils decidedly agree in the characters which have been here assumed for this

genus.

Soon after the discovery of these fossils, Miss Benett, whose exertions have much aided this department of natural history, favoured the Geological Society with a suite of drawings, and of fossil specimens of various forms, but decidedly of this genus, which had been found in the sand, chiefly in the neighbourhood of Warminster. This valuable collection is rendered extremely interesting, by the great variety of forms which these fossils have assumed; cylindrical, straight, ramified, round, oblong, ovoid, wide and narrow, short and long, cup or funnel-formed; elongated like a cucumber, as in Organic Remains, vol ii. Pl. 10. fig. 6; tulip-formed, exactly agreeing with those discovered by Mr. Webster, and assuming also the forms of spongia turgida, sp. alcicornis et damicornis, and indeed many other of those forms which sponge offers to our observation. Among the most interesting specimens are those which are lobated, and in which from two to five or six lobes, closely united together, are found upon one stem; and in one specimen, two stems arise from the same base, one of which terminates with three and the other with four lobes.

Flints are sometimes found of a roundish form, pierced internally with numerous tubules passing in every direction, and giving the idea of the flint having invested a small hispid leafless shrub. It is extremely probable that these fossils may have originated in a species of this genus, bearing this form, and having the tubuli thus radiating

* Geological Transactions, vol. ii. The importance of this discovery of Mr. Webster will be observed, when it is considered that the remains of this animal, known perhaps only in this formation, are found in considerable numbers in the Leith Hill of Surrey, in the green sand of Wiltshire, Devonshire, &c. and in the freestone of Portland.