of the Beeston seam: this has since been examined by M. Agassiz, who pronounced it to be a portion of the large tuberculated scale of some species of fish.

In the main limestone at Ardwick was found a specimen so exactly resembling the one from Leeds, that the drawing would almost serve for a representation of either. The only difference I am able to perceive is, that the marginal portion, which in the Leeds specimen is smooth, in ours is slightly tuberculated. It is also of an irony colour, whilst the other is described as being of a bright glossy black. The specimen was presented to the Society by Mr. Francis Mellor, the director of the Ardwick lime-works.

In one very thin seam passing through the black bass, the position of which is generally marked by a line of pyrites, are found remains of a small species of fish, much crushed, the fragments being all detached.

Of the scales I possess several forms: they are generally small, rhomboidal, and of a bright glossy black, often corrugated on the surface. Others are arrow-shaped, about one third of an inch long, having a depressed sulcus passing along the centre especially at the broad extremity, and irregular striæ towards the apex. A third form, very thin, irregular in size, and marked with dots and undulating lines, I at first mistook for palates, but on comparing them with a specimen of a Palæoniscus from the copper slate of Eisleben, I was enabled to determine to what portion of the fish each scale belonged the thin undulated ones are portions of the reticulated covering of the head; the rhomboidal, some smooth and some corrugated, belong to the body; and the larger arrow-shaped ones have formed a single line along the dorsal ridge, from near the dorsal fin to the insertion of the tail. I cannot venture to say that they are of the same identical species, but they certainly approach very near in their characters.

In one instance I found part of a small jaw-bone of some species of fish, which may have some connexion with the scales above described: it is about 3rd of an inch in length, and is furnished with a regular row of obtuse, glossy black teeth, eleven or twelve in number, and about th of an inch in length. It is from the black bass.

The same fruitful seam contains strong bony rays, similar to what we often find supporting the large dorsal fins of many species of fish. They are generally depressed, although we occasionally meet with them in their original rounded form. I have one specimen 2 inches in length, but which must have been considerably longer.

The most singular fossil I have yet met with is a specimen Third Series. Vol. 9. No. 55. Nov. 1836.

2 T

from the black bass, and evidently connected with the teeth of fish. Attached to a peculiar round body are two teeth (?) about half an inch long, with the two lateral cutting edges finely denticulated: they are separated about 7th of an inch at their base, but diverge until their points are nearly half an inch asunder. I only know one portion of a fish to which this singular fossil could belong, and that is, the apex of the upper jaw. In many species of foreign fish are two teeth in that situation which diverge as in our specimen, and this must have been of a similar nature. It may belong to the same species as the long rays*.

In the roof of the Four-feet mine, Professor Phillips has been so fortunate as to discover remains of Megalichthys Hibbertii, a fossil which is now apparently diffused through several of the limestones of the coal series: Mr. Mellor has in his possession a beautiful specimen of a lower jaw with a row of five teeth, with several other fragments. These are generally indistinct and ill defined in their outlines. With the exception of Mr. Mellor's beautiful jaw, the finest specimens of this interesting animal have fallen into the possession of Professor Phillips, who will doubtless, in his expected paper at the meeting of the British Association, give a detailed account of them, and their affinity with specimens from other districts which I have not had an opportunity of examining.

The following catalogue comprehends such remains as we have now discovered in and above the third or main limestone:

Planta.-Neuropteris cordata, Pecopteris, Sphenophyllum, Sphenopteris linearis?, Cyclopteris, Lepidodendron Sternbergii, Stigmaria ficoides, Calamites decoratus, Calamites nodosus, Asterophyllites.

Mollusca.-Planorbis, Unio, unknown Bivalve ?.
Entomostraca.-Cypris, Daphnoïdea?.

Ichthyolites.-Palæoniscus (scales and teeth). Teeth, opercular bone, and rays of an unknown species. Megalichthys Hibbertii (scales, lower jaw, teeth, &c.).

SECT. IX. General Results and Inferences.

From these detailed descriptions and simple facts, we may draw a few inferences as to the nature of the limestones and the circumstances under which they have been deposited.

This group of limestones has hitherto, as I before observed,

* Since the above was written I have discovered a second specimen of this most interesting fossil, closely resembling the one described, with the exception of being rather smaller it throws no new light upon its nature, except exhibiting a small rounded tooth or process, about 4th of an inch long, fixed between the other two. At the same time I found an opercular bone, probably connected with the same species.

+ Since then I have found a large scale of this animal in the black bass, of a rhomboidal form and closely resembling the scales of the thigh of the American alligator.

been confounded with the magnesian limestone, which latter stratum had never been distinctly identified in this neighbourhood, until an examination of the fossils of Collyhurst led me to the conclusion, that the clays and thin limestones there exposed were the representatives of that series, so important in Yorkshire and Durham. On comparing the fossils of the magnesian series with those from Ardwick, we shall find that no one species found at the latter place agrees with any yet discovered in the magnesian limestone in England, the strongest evidence that they do not belong to the above series of rocks. The small fish bears a considerable resemblance to the Palæoniscus from the copper slate or zechstein, a stratum concerning the relative position of which I have some doubt.

On comparing the fossils, however, with those from the carboniferous system, we immediately observe their identity: we have Stigmaria ficoides, the almost universal characteristic of the coal measures of Lancashire and Yorkshire; several Filices, especially a Sphenophyllum, a genus, I believe, confined to the coal series; Calamites, and the still more important leaves and stems of the Lepidodendron Sternbergii. However undecided we might be previously, the discovery of these remains cannot leave the slightest doubt as to their connexion with the carboniferous group.

The merit of the discovery of this important generalization belongs to Dr. Phillips, who, in May last, explained his views to the section of the Manchester Philosophical Society, and expressed his firm conviction that geologists had hitherto been in error in connecting these limestones with the magnesian series; and the deciding upon the relative position of so large a mass of strata, in such close connexion with the Lancashire coals, cannot be viewed otherwise than as an important result.

On a slight examination of the fossils, we observe another important fact: no marine remains whatever have yet been discovered. When we find freshwater remains mingled with those of marine origin, the probability is that the deposit was formed in some estuary or mouth of some large river; but here the remains are entirely of freshwater origin. All the most important fossils which guided Dr. Hibbert in arriving at his splendid results at Burdiehouse, we find here. The entire absence of marine remains: the extreme abundance of microscopic freshwater Entomostraca, of Unionidae; fish of the genus Palæoniscus; minute univalves, in all probability of the freshwater genus Planorbis; and lastly, the discovery of remains of Megalichthys Hibbertii, all concur in assigning to the limestones a freshwater origin. It would be needless for me to enter here into any long discussion on the nature of freshwater

limestones, or the manner and circumstances under which they have been produced, as that has been done in so masterly a style by Dr. Hibbert, in his memoir on the Burdiehouse limestones and the fact of the occurrence of freshwater limestones in the carboniferous group has become so firmly established, that what remains to be done is a careful investigation of the districts where the coal measures are exposed, in order to trace how far they extend, and what varieties of remains of animal life they present. The ultimate result, I have no doubt, will be a vast mass of evidence respecting the circumstances under which the coal measures generally have been deposited, and a considerable additional light will thus be thrown upon the origin and formation of the coal itself. Thus, as the small mountain rivulet, receiving new force and power from the most insignificant sources, gradually rolling on towards the wide ocean, becomes the broad and noble river, so each new fact, however trifling in itself, will give a slight but additional impetus to the stream of knowledge which is fast bearing us forward to the ocean of some grand theory of geology: the collection of facts thus slowly accumulated will one day be grasped by some comprehensive and master mind, -a new Newton will arise and place in our hands one universal outline of the laws that have guided and still guide nature in her unvarying progress.

Hall of Manchester Natural History Society,

August 12th, 1836.

W. C. WILLIAMSON.

LXIX. On the Beds immediately above the Chalk in the Counties near London. By JAMES MITCHELL, LL.D., F.G.S.*

THERE is a description of flints found in beds immediately over the chalk, and below the sand, in all the places where these strata are seen to meet, in the counties of Surrey, Kent, Essex and Hertford, and may very probably also be found in other counties, also in similar situations.

There are sixteen localities in which I have seen this flint on the south side of the Thames, and five on the north side. The pits on the south side are:

Pit close to Croydon in Coomb Lane.

Road to Tunbridge beyond Farnborough.

Pit on the right of the road from Bromley to Chiselhurst. Pit in a vale on the south side of Elmstead near Chiselhurst.

* Communicated by the Author.

Loam-pit hill near Lewisham.

Mouth of the Cavern on the side of Blackheath hill.

Pit in Old Charlton on the south side of the Woolwich road. Great pit at New Charlton.

Cliff opposite Woolwich dock-yard.

Pit at Erith.

Three pits near the bank of the river Cray near Crayford. Pit on the north side of the churchyard at Dartford.

Trenches dug for forming a common sewer near Gravesend, on property belonging to Mr. Rosier.

The entrance to the tunnel of the Thames and Medway canal at Higham.

On the north side of the Thames the localities observed are, Purfleet, a pit on the west side and another on the east side of Belmont Castle near Grays, and a pit on the east side of Grays; also a pit at George's Farm near Hertford.

A similar stratum is seen at Newhaven in Sussex, and the same flints have been seen in other counties, but not in their original site.

At Purfleet the name given to these flints is iron flints. The bed in which they are found is generally about eight or nine inches deep, seldom above a foot, and consists of a reddish clay with an abundance of oxide of iron. Scarcely any sand can be got from this clay by washing. It is stuck quite full of flints. Some of these flints are very small, not exceeding an inch in length; but the greater portion are three or four inches long, and some much longer. They are round, and terminating in a point at each end, and on the whole in form not unlike a cucumber. Some however are of a triangular form. The exterior is covered with a rough black crust, which is found to be a combination of silex and oxide of iron. When broken by the hammer the oxide of iron is found to penetrate about a quarter of an inch all round, and there are frequently streaks of iron further in the interior. The body of the flint is black, but decidedly distinct from the dark blue flints found in chalk. The fracture is conchoidal, but these flints, though not unmanageable, do not yield flakes in any direction so readily as the chalk flints. When burnt in the fire the exterior crust becomes reddish, and the rest of the flint is of a dirty white colour, not nearly so bright and beautiful as the porcelain substance made by burning chalk flints. It is exceedingly difficult, with ever so great caution, to get them burnt without cracking and flying in pieces. Such of these flints as have been exposed to the atmosphere have become partially decomposed immediately under the black crust.

I have been informed by two gun-flint makers that such