cartilage when rotated with the thyroid, whereby the antero-posterior diameter of the larynx is enlarged and the vocal ligaments stretched from a d to ae. f. The chink between the thyroid and cricoid cartilages. The dotted line represents the closing of this chink when the cricoid is rotated on the axis of motion of these cartilages at the point d.

Bernard Street, Brunswick Square, June 7, 1836.

LXVIII. On the Limestones found in the Vicinity of Manchester. By W. C. WILLIAMSON, Curator of the Museum of the Manchester Natural History Society.

A

[Continued from p. 249, and concluded.]

SECT. VII.-Other Localities where Limestones are exposed. T two more localities limestones have been pointed out to me by Dr. Charles Phillips, who has contributed so much towards the elucidation of the geology of this district; both of these were exposed by the cutting of the Liverpool and Manchester Railway. One of these is at the base of the Sutton inclined plane on the Manchester side, and the other near Whiston, on the opposite side of the hill, forming two of the points which guided Mr. E. Hall in laying down the range of the magnesian limestone, with which he confounded them.

That at Whiston is exposed for about seventy yards, and forms a seam six feet thick, but which never rises more than nine feet above the level of the railway and is covered for some extent by a series of solid sandstones. The top of the limestone consists of a greenish conglomerate, below which is presented the reddish conglomeroid structure peculiar to the Ardwick limestones, and the lower portion of the seam is composed of the solid gray limestone common at the above locality.

From its so strongly exhibiting the peculiar mottled appearance, I am of opinion that it will correspond with the uppermost or four-feet seam at Ardwick. This is in some measure confirmed by the occurrence of the same minute turbinated shells (Planorbis?) found in the Ardwick series; but as no borings have been made on the spot, I cannot be certain as to what exists below.

The limestone at Sutton I cannot identify with any exposed at Ardwick, although in its appearance and fracture it resembles the thin one of two feet below the main limestone on the bank of the Medlock. It is only about a foot thick, and rests upon a long range of the coal shales, which are very well exposed, exhibiting many partial faults and thin coal seams.

As I before described, at Collyhurst we have the magnesian limestone laid bare for a small space; and about half a mile

further, on St. George's Road, the coal measures appear at the pits of E. Buckley, Esq. According to the regular range of the strata, we ought to find the Ardwick limestones exposed between these two points, but they do not appear: on an examination of the locality, the reason is obvious; the red sandstone ranges unconformably with the coal strata, overlying their outcropping edges, and thus completely covering up that portion in which the limestones ought to have been met with. The locality is a very difficult one to examine and decide upon, from the want of sections at the most important points; but as there is no doubt of the sandstone overlying the edges of the coal strata, and the dip of the latter being such as would carry their upper portions beneath where we find the red sandstone on the surface, the apparent deficiency is accounted for.

SECT. VIII. Organic Remains.

The fossil remains of this series of limestones, with one or two exceptions, are neither numerous nor exhibiting much variety, although they are of a peculiar character: these we will examine in their separate classes, and then from their evidences endeavour to draw some conclusion as to the nature of the limestones and the circumstances under which they were deposited.

1. Vegetable Remains.

These are not so numerous as, from the connexion of the strata with the coal measures, might have been expected, although further investigation will doubtless bring new deposits to light.

Stigmaria ficoides is found abundantly in the seam of coal immediately below the black bass. The coal appears to have been entirely composed of this plant, as it is the only one I have hitherto found in connexion with it. The character this extraordinary plant must have given to the primeval world cannot fail to have been highly singular, as from the highest to the lowest coals of this group of strata its abundance generally forms a conspicuous feature, whilst its range appears to have been almost universal. In a seam of indurated blue clay, below the black bass, the leaves of Stigmaria are found in the greatest profusion. The same is observed in a reddish clay on the bed of the Medlock, much lower in the series.

In the blue clay, immediately above the black bass, I found a small and beautiful species of Sphenophyllum, much like Sphen. erosum, but with broader leaflets, and fewer in each whorl. In the same clay occurred fragments of a species of Pecopteris and also of an Equisetum, neither of which I was able to preserve.

In working through a narrow passage of one of the mines,

used only as a drain to carry off the water from the pits, Mr. Mellor and myself were rewarded by the discovery of a thin seam of red shale, about sixty feet above the main or three yards limestone, filled with the most beautiful remains of plants, which fully confirmed the opinion Dr. Charles Phillips had been the first to form and advance. Amongst these were large specimens of Calamites decoratus, Brongn., and Cal. nodosus; stems of Lepidodendron Sternbergii, an elegant species of Neuropteris* with large leaflets, a small Cyclopteris, leaves of Stigmaria ficoides, fragments of a Pecopteris, Asterophyllites, and several other plants common to the coal series below, forming a character which, if any truth exists in the theory of identification, cannot for a moment be mistaken.

2. Mollusca.

These, like the plants, are not of numerous species. In the three limestones worked at Ardwick, and also at Whiston, but most abundant in the Three Yards mine at the former locality, are countless myriads of a small depressed turbinated shell, the merit of the first discovery of which is due to Professor Phillips, who is at present investigating its nature. It bears the strongest resemblance to a Planorbis, and is evidently of a nature very similar to the one found at Burdiehouse, by Dr. Hibbert, and figured in his memoir (page 13.). In form it closely resembles the recent Planorbis Nautilus (Fleming,) but is rather smaller. It occurs, as I said before, in all the limestones worked, and Dr. Phillips found the same fossil in the limestone at Whiston, and also in a fragment of shale from the colliery of E. Fitzgerald, Esq., at Pendlebury, about four miles from Manchester. It was found in sinking down from the upper or "two-feet coal" to Buckley's "three-quarters mine," the highest coal of any importance in the Lancashire coal-field.

The black bass is literally filled with fragments and perfect shells of a species of Unio of small size. It bears a considerable resemblance to Hibbert's Unio nuciformis from the Burdiehouse limestone, but is of a less globular form. This shell varies considerably in size, being sometimes one and a half inches in length, and at others not more than three quarters of an inch. The depressed and crushed state in which these fossils are found would indicate a shell of a thin and fragile nature, and such it has doubtless been: they are most fractured towards the lower portion of the bass, no perfect ones being there observable, but towards the top they are generally uninjured, further than has been the result of pressure. Of

This I find to be Neuropteris cordata, which Dr. Phillips has since met with in the coal measures at Oldham.

this shell, I found a single specimen in the blue clay which contained the Sphenophyllum; and in one of the thin seams of red clay, above the first limestone, they are also to be met with, though of a smaller size. Dr. C. Phillips found them at Pendlebury, in the fragment of shale containing the Planorbis. This was the circumstance that first induced the above gentleman to differ from former observers in his opinion as to the relative position of the Ardwick limestone, separating it from the saliferous and connecting it with the carboniferous group of rocks, an opinion of the correctness of which there remains not the slightest doubt.

My friend Mr. Joshua Alder, of Newcastle, informs me that he has met with an Unio, closely resembling our specimens, in the coal strata at the above place. This shell differs from the U. nuciformis of Burdiehouse in being broader and wider in proportion to its length, as well as in being a more fragile and delicate shell. I am inclined to think it is an undescribed species; if so, I would propose the name of Unio Phillipsii as a slight return, not only for the private kindness I have met with from Dr. C. Phillips, but for the service that gentleman has done to geology by his indefatigable exertions in investigating the nature of these limestones, as well as being under his guidance in a district new to me when I first discovered this most characteristic shell.

Towards the upper portion of the third limestone is found a thin seam of comminuted fragments of shells, amongst which may occasionally be found traces of more perfect specimens. These bear a close resemblance to, if they are not absolutely the same as, the fossil now under consideration. From the several localities where these shells are found, and from their extreme abundance, combined with the rarity of other Mollusca of equal size, they must have formed an important feature of the fresh waters of that early æra.

In the blue clay, immediately above the black bass, are a series of remains, in attempting to decide upon the nature of which I find myself completely puzzled. They are very thin bodies of a brown colour, nearly square in their form, two of the corners being angular, and the opposite one rounded: I have some nearly a quarter of an inch across. At first I imagined that these were scales of fish, but now think they must be same bivalvular shell. Their surface is marked with strong concentric ridges, and passing from the hinge (?) to the opposite corners, are two diverging elevated lines. I cannot detect any traces of teeth, but have found several specimens in which the two valves (?) were connected at the hinge, and the four ridges commencing from one common point in the centre and diverging two each way: these I pointed out to

Professor Phillips, who will perhaps be able to lay before the public some more decided opinion as to their nature.

3. Entomostraca.

Microscopic fossils are always with difficulty assigned to their proper situations in the scale of organized life. This difficulty was experienced by Dr. Hibbert amongst the Entomostraca of Burdiehouse, and as a necessary consequence, we experience the same amongst those of Ardwick. Throughout the whole extent of the black bass, but especially amongst the broken Unionidae near the seam of coal, we find abundance of minute remains, generally about th of an inch in length, which can only be assigned to the above-named group of Crustacea. I am uncertain whether there are one or two species: if two, the one will be a Cypris, approaching very closely to Cyp. Faba in its beanlike form, but rather more elongated: the chief objection is, our not being able to detect the hinge. The other species, if different, is in reality subunivalve, with a lateral opening on one side: this is closely allied to the recent Daph nia, and is probably of Hibbert's genus Daphnoidea. It is of the same size and outward form as the one above described, of which it may only be the opposite side, showing the natural groove: when largely magnified, I cannot compare it to anything better than the berry of the coffee-tree after it is burned. To judge from the drawings Dr. Hibbert has given, I think our Daphnoidea presents the lateral opening much more distinctly than any he has observed, from which ours differ in being perfectly smooth instead of granulated.

From these remains we have, without any other evidence whatever being wanted, a strong proof of the freshwater origin of this portion of the series.

4. Remains of Fish.

We now come to the group of remains which first attracted my attention in the limestones of Ardwick. In June 1835 I first detected remains of fish in the black bass, and have since then at various periods made new additions to my collection. As we have in no one instance discovered a perfect specimen, the difficulty of identifying them with any known species must of necessity be great, especially as they are in such a crushed state that not even two scales can be found preserving their relative positions.

In the fifth number of the Zoological Journal, published April 1825, is a drawing and description, by the late amiable and talented E. S. George, Esq., and J. D. C. Sowerby, Esq., of a remarkable bony plate, which the writers imagined to be a portion of the palatal bone of some fish, found near Leeds in the seam of coal commonly known in Yorkshire by the name