selves; but the young specimens as well as the old, are subject to great variety in character.

Some of the cup-shaped sponges attain a large size; I have one which measures 12 inches in diameter.

Many specimens in my possession exhibit characters which apparently indicate new species, besides those about to be described. I have however thought it best only to give an account of such as are sufficiently perfect to afford a distinct idea of the character.

SIPHONIA.

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1. Siph. clava.-Club-shaped; gradually increasing in size till very near the crown: the larger canals, after spreading widely in the substance of the body, are crowded together at the top, presenting a pentagonal, or hexagonal appearance. Fig. 2.

The shape of this species is very regular, as will be seen from the annexed figure, (fig. 2.); the original is seven inches in length: the stem is pierced by a single canal, for about an inch and a half from the bottom: about an inch higher, four or five principal canals, and several smaller ones shew themselves; the subjoined sketch, (fig. 3.) drawn of the natural size, will give some idea of the appearance: still higher, the canals increase in number, and are considerably spread in the body of the fossil.

At the crown there seems to be a still greater number, and they are so crowded, as almost to represent a honeycomb; figure 4, which is drawn of the natural size from a specimen a little ground down at the top, will give some idea of this arrangement.

In specimens which have been rolled on the beach, and which are consequently without the external covering, the whole surface appears studded with minute pores; these are the orifices of small radiating tubes, which communicate with the larger canals.

This species does not appear to be

very rare.

2. Siph. anguilla.-Elongated, cylindrical, nearly of an equal size throughout; length equal to eight or more times the breadth; larger canals not crowded at the summit. Fig. 5.

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Fig. 5. which is reduced from a specimen thirteen inches in length, will shew the general form of this species: the bottom is pierced by a single canal, which about an inch and a half higher, appears divided into eight or ten: this number is not materially encreased at the top, where the canals are scattered over the surface, and not crowded together as in the last species: the annexed figure, (fig. 6.) which is of the natural size, shows the appearance of the summit: it will be seen, that the highest part is of a less size than the rest of the

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fossil, and forms a sort of crown. The specimen figured is considerably compressed, so that in the sketch it appears broader in proportion to its length than it would have done had it been of its natural form.

This species is rare: besides the specimen from which the above description was taken, I have

only met with two or three fragments.

SPONGIA.

1. Sp. catablastes.-Inversely conical, with a considerable depression at the crown: from ten to fifteen arms projecting downwards from the lower part of the body. Fig. 7.

Of this beautiful fossil, (fig. 7.), only one specimen has hitherto been discovered: but as the characters are very well marked, it will not, I hope, be thought premature, to consider it a new species. Nothing can be said respecting the length of the stem, as it had unfortunately been lost when the specimen was taken from the face of the cliff: the whole body is covered with irregular depressions, which on the superior surface, and in the neighburhood of the side arms, take a flexuous

appearance: neither the stem, nor the side arms appear to have had any central perforation. The original is nearly six inches in length.

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2. Sp. fastigiata. The lower part funnel-shaped, inflated; the upper part a cone, rising from a slight depression. Fig. 8.

This fossil is not by any means common; I have only seen two specimens, of which the most perfect is represented in the annexed sketch. (fig. 8.) The inferior part is surrounded by depressed undulated lines, some of which take a diagonal direction: the terminating cone is small, and not by any means proportionate to the inflated appearance of the lower part: the central cavity appears to be very small indeed.

The figure is about one half the natural size.

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3. Sp. sepiaformis.-Irregularly funnel-shaped : marked externally with a few scattered elevated orifices; from eight to ten arms, rising upwards from the superior edge: one or more additional branches arising from the same root. Fig. 9.

This beautiful species appears to be extremely rare: besides the specimen represented by the figure, (fig. 9.) I have only met with two or three fragments, which still were sufficient to convince me that the above characters were not accidental: the length of the fossil from the root to the extremity of what remains of the longest arm, is about eight inches: there is an appearance of one small side arm, thrown off downwards, but most probably this is not a constant character: the root does not appear to have been very fibrous.

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4. Sp. ampulla.-Bladder-shaped, covered with irregular depressions; stem equal to the body in length; fibres of the root short and thick; central cavity cylindrical, half the depth of the body. Fig. 10.

This species is not so rare as the preceding, but is seldom met with in such complete preservation as the specimen figured, (fig. 10.); the greater number of those which have been found, are compressed and distorted. Two or three weathered specimens in my possession show very clearly that the central cavity is in the shape of a short, thick cylinder, suddenly terminating about the middle of the body: the length of the specimen is about nine inches and a half.

5. Sp. spinosa.-Globular, unattached, covered partly with oval notched plates, overlying each other, partly rough, covered with irregular depressions: armed with from eighteen to twenty spines: internal structure fibrous, radiating from a point in the circumference. Spines varying much in size, hollow, covered with an appearance of pointed scales overlying one another. Fig. 11.

This most singular fossil has I believe, only been found in two localities; one of which is the cliff about a hundred yards west of the Danes' Dyke, and the other a quarry north of Marton, probably where the same bed appears on the surface. It is rare; I only know of five specimens, of which one was found by my friend Mr. W. H. Dykes, and is now in the Museum of the Hull Literary and Philosophical Society. I have indeed heard of a fossil in the collection of Mr. Bowerbank, which from the account given to me by Mr. Charlesworth, may probably be the same species, but I have never been fortunate enough to obtain a sight of it.

The general appearance, when most perfect, is that of a small Cidaris, with the spines attached: when imperfect, it would probably be taken for one of the small globular sponges,

16 UNDESCRIBED ZOOPHYTES FROM THE YORKSHIRE CHALK.

so common in the chalk near Bridlington, which may perhaps account for its not having been before noticed.

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12

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The annexed (fig. 11.) will give some idea of its general form. The specimen drawn (fig. 12.) is one which was found on the scar, and having been water-worn and weathered, shows the internal structure; the figure, which is a little magnified, displays the fibrous structure rather more plainly than is seen by the naked eye, but when a lens is applied, the radiating structure becomes very apparent. The structure of the spines is very singular; at the base, they seem composed of an aggregation of little spiculæ, which afterwards are so arranged as to give the appearance of a series of furrowed, pointed scales. Fig. 13. represents the lower part of one of the spines very higly magnified.

The covering of the body is of a peculiar character; in some places it appears similar to that of many other sponges, marked with indefinite depressions; in others, there are very decided oval notched or jagged plates, most of which overlie one another; this arrangement is generally seen most distinctly in the neighbourhood of the spines. Fig. 14 repre

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sents a portion of the covering very highly magnified. From the singularity of this appearance, the animal might almost be supposed to belong to a very different class from that of the sponges, and the associated genera; so at least it appeared to me, till, being anxious to see more of the internal structure, I had the specimen cut through, just below the plates figured in the last diagram: an irregular fibrous structure then became visible, similar to that shewn in (fig. 12.) with the exception of the radiated appearance: this difference however may be accounted for by its being a cross section. Under these circumstances, as the spongy structure appears to be constant, while the plated appearance is not so, I have placed it amongst the sponges till it shall have been examined, and its place assigned by some more experienced naturalist.