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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
the crown: the larger canals, after spreading widely in the substance
nal, or hexagonal appearance. Fig. 2.
from the annexed figure, (fig. 2.); the original is
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.
throughout; length equal to eight or more times the breadth ; larger
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 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. 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
part a cone, rising from a slight depression. Fig. 8. 8
This fossil is not by any means common;
The figure is about one half the natural
3. Sp. sepiaformis. Irregularly funnel-shaped : marked externally with
a few scattered elevated orifices; from eight to ten arms, rising up-
This beautiful species appears to
4. Sp. ampulla.--Bladder-shaped, covered with irregular depressions ;
stem equal to the body in length; fibres of the root short and thick;
This species is not so rare as the pre-
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,
earance hrown as probah character
ar to hare
16 O'NDESCRIBED ZOOPHYTES FROM THE YORKSHIRE CHALK.
so common in the chalk near Bridlington, which may perhaps account for its not having been before noticed. 11
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 repre14
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.