Wenlock Limestone Research Articles

British Fossil Cephalopods

FOR the first time has just appeared Part 1. of a monograph upon the British Palæozoic Tetrabranehiate Cephalopoda, and important as this group of Mollusca has ever been regarded by all palæontologists and badly as such has been wanted by all students of British Palæozoic geology, no one has hitherto attempted any history of this group for Britain. Barrande has elaborately done so for Bohemia and De Koninck for Belgium, both have extensively written upon the older Cephalopoda [Cambrian, Silurian, Devonian, and Carboniferous]. Barrande in his exhaustive work illustrates no less than 1620 Silurian species. De Koninck in his last important work upon the Carboniferous Limestone of Belgium enumerates 170 species, amongst them many new forms and many common to British strata. Prof. J. F. Blake intends completing this history of the British Palæozoic Cephalopoda in two volumes. The part now issued, being part or vol. i., treats only of Silurian species. No kss than 244 quarto pages and 31 plates are devoted to the description of 11 genera and 6 sub-genera, and 143 species. The great genus Orthoceras being illustrated by 76 species, and its 4 sub-genera by 6 species, Cyrtoceras 23 species, Poterioceras 2, Gomphoceras 11, Phragmoceras 7, Ascoceras 3, Nautilus 4, its sub-genus Trochilites 3, Trochoceras 12, Lituites 2, Ophidioceras 2, and Goniatites (?) 2 species. These 143 species range from theTremadoc Rocks, of the Cambrian series, to the Tile-stones of the Upper Ludlow. Forty of the 145 species also occur in Europe and America, or 32 are common to Europe and 6 to America, thus showing the wide distribution of certain genera and species. Thirty-one plates accompany the letterpress or text, every species being figured, and more than 2000 specimens have been examined by the author having reference to the history and description of these 143 species. Prof. Blake has given on pp. 233–6 a table of the distribution in time of all the species, and on p. 237 a condensed table showing the “growth, culmination, and decay of the genera and group.” These two tables are suggestive, and the outcome of their study shows that there were two maxima of individual abundance, one occurring in the older group of rocks, the Caradoc or Bala, and the other, in the Lower Ludlow, yet we feel assured that there was no real diminution or falling off in the variety of forms between these two deposits. The tables clearly show that the species in the Wenlock Limestone were (or are now found to be) comparatively few as compared with those in the shales above and below, and would indicate that the Cephalopoda of the Wenlock seas were not commonly frequenters of clear and shallow waters, but were partly pelagic and possibly gregarious in more or less turbid waters, as indicated by the impure sediments composing the Ludlow shales.

Notes on the Polyzoa of the Wenlock Shales, Wenlock Limestone, and Shales over Wenlock Limestone. From material supplied by G. Maw, Esq., F.L.S., F.G.S.

The organisms found in the Wenlock Shales of Shropshire have been already alluded to by Mr. Maw and by Mr. Davidson in their joint paper in the ‘Geological Magazine’ for the year 1881. The remarks of these authors bore chiefly upon the Brachiopoda found in the shales; but the other organisms were casually alluded to in passing. Since this joint paper was written, I have had an opportunity of working over nearly one hundredweight and a half of the débris, and this, in all probability, may represent from six to eight tons of the unwashed clay. My object in searching was principally to pick out the Polyzoa and the smaller Actinozoa of the débris; but in doing this I felt very reluctant to pass over organisms which belonged to other than these two classes; consequently, to some extent, my collection consists of specimens illustrative of the Actinozoa, Echinodermata, Annelida, Crustacea, and Brachiopoda, as well as the Polyzoa of the shales. It is not my intention in the present paper to commit myself to remarks on the genera belonging to these classes otherwise than by presenting a Table of the whole series of associated fossils. This Table is divided into twelve columns, eleven of which are allotted to the several localities from which Mr. Maw supplied me with material; the other column affords me the opportunity of completing the range of species by recording their presence in the Wenlock Limestone.

On the Predevonian Rocks of Bohemia

Summary In very many of the Predevonian rocks of Bohemia we find marked lithological resemblances to the corresponding horizons in Britain. The Precambrian series is divisible into two distinct groups, similar to the Dimetian and Pebidian groups of Britain, and lying unconformably to one another and to the overlying Cambrian rocks. The beginning of the Cambrian period is marked, as in Britain, by a coarse conglomerate, which is probably of later formation than that of our own island, although it is probably homotaxeous with it. Moreover, there are strong resemblances between the various bands of the Bohemian and British Cambrian beds, especially marked in the deeper water deposits. The palæontological similarities are in many cases not so striking as the lithological. In the Silurian period, the resemblances, both lithological and palæontological, between Bohemia and Britain were less striking than in the Cambrian. The limestones so abundant in the Bohemian series seem to be lenticular masses having no wide extension; the most regular limestone is that of E 2, and this is about the horizon of, and comparable with, the Wenlock Limestone. But although the beds of this period as a whole are not so strictly comparable in the two countries as those of the Cambrian, we nevertheless find most remarkable coincidences between the zones of the lowest band, i. e. the Graptolite- bearing shales. The igneous rocks do not present many unusual features; but the occurrence of mica-traps in the Cambrian beds is very noteworthy, limited as they are, so Objection may be raised to my using Prof. Sedgwick’s nomenclature for the rocks of a region which M. Barrandehas so conclusively shown to possess three well-marked faunas. But the foregoing observations seem to show that. the break between the upper and middle faunas is much more marked than that between the middle and lower. In the first place, the deposition of the Cambrian beds does not seem to have begLm over the whole area until thG close of the Primordial era, the rocks containing the Primordial fauna, as well as the underlying conglomeratic series, being only locally developed, whilst it is not until the overlying beds of d 1 a that any thing like continuous deposition appears to have set in. Again, if I am right in referring d 1 α & β to the Lingula Flags and Tremadoc Slates respectively, the unconformity between the Primordial zone and second fauna of Bohemia does not occur at the same horizon as that between the Primordial zone and overlying beds of Britain, for the equivalents of d 1 α & β are included in the Primordial beds of Britain, or Cambrian of Sir C. Lyell, Dr. Hicks, and Mr. Lapworth. The break between the second and third faunas of Bohemia, on the other hand, occurs at the same horizon as in Britain, viz. between the top of the Bala beds and the Graptolitic fauna of Birkhill age. Lastly, the beds of d 1 α & β have as yet yielded by no means a satisfactory fauna, so that we do not here get one fauna in beds immediately succeeding another, as is the case with the beds at the top of the second and base of the third faunas of M. Barrande. But the connecting link between these two latter periods was supposed to have been discovered in the colonies of M. Barrande. I feel justified in saying that I have brought forward sufficient evidence to warrant a reconsideration of the data on which the theory of colonies was founded, and to give some grounds for the supposition that they are only portions of the band e 1 faulted down among the grits and shales at the summit of the Cambrian series.

On a new Genus of Silurian Asteriadæ .

Abstract The specimen described showed the outline of a small Starfish, with a large disk and short rays, in a slab of Wenlock Limestone from Dudley. The outline of the ten rays was described as marked out by the border of small triangular spines, the other plates of the disk and rays being absent. Each ray was terminated by a stem-like multiarticulate process as long as the ray, from towards the extremity of which spring slender lateral processes, giving it a tufted appearance. This Starfish, which is in the collection of Dr. Grindrod, F.G.S., is named by the author Trichotaster plumiformis .

Societies and Academies

LONDON Geological Society, May 14.—Mr. Joseph Prestwicb, F.R.S., vice-president, in the chair.—The following communications were read.—“On the genus Palæcoryne, Duncan and Jenkins, and its affinities,” by Prof. P. Martin Duncan, F.R.S.—In this paper the author referred to certain minute fossils from the Carboniferous rocks of Scotland, described by himself and Mr. Jenkins in a paper read before the Royal Society, as belonging to the Hydroido, and most nearly resembling the recent genus Bimeria, Wright. He stated that numerous specimens since received threw some further light on the nature of these fossils, and showed especially that ice all probability the base is not really cellular, but that the cellular appearance is produced by the growth of the real base of the polype over the cells of the Fenestella on which it grows.—“Notes on Structure in the Chalk of the Yorkshire wolds,” by Mr. J. R. Mortimer.—In this paper the author described a peculiar structure observable in chalk from Yorkshire and elsewhere, giving it a striated appearance. This structure bad been ascribed by Dr. Mackie and others to slickensides. The author adduced reasons for doubting the mechanical origin of these striations, and argued that they are of an organic nature. He ascribed them to corals, and remarked that similar striæ occur in all limestone formations.—“On Platysiagum sclerccephalum and Palæospinax priscus, Egerton,” by Sir P. de M. Grey-Egerton, Bart., M.P., F.R.S.—The two species of fossil Fishes noticed in this paper were described by the author in the 13th Decade of the Memoirs of the Geological Survey, published in 1872. They are both from the Lias of Lyme Regis. He now described some new specimens which add to our knowledge of their characters. An example of Platysiagum shows the position of the dorsal fin, which is placed very far back, occupying a place opposite to the interval between the ventral and anal fins, end the form of the trunk, which is of nearly uniform depth from the occiput to the base of the dorsal fin. The structure of the dorsal fin was described in detail. The new specimen of Palæospinax priscus shows especially the position of the second dorsal spine, which is placed over the 50th vertebra, the first being on the 16th, the fish thus most nearly approaching the existing Cestracion, which it also resembles in its dentition. In other respects it seemed to be most clearly allied to Acanthias.—“On a new genus of Silurian Asteriadæ,” by Mr. Thomas Wright, F.R.S.E.—The specimen described showed the outline of a small Starfish, with a large disc and short rays, in a slab of Wenlock Limestone from Dudley. The outline of the ten rays was described as marked out by the border of small triangular spines, the other plates of the disc and rays being absent. Each ray was terminated by a stemlike multiarticulate process as long as the ray, from towards the extremity of which spring slender lateral processes, giving it a tufted appearance. This Starfish, which is in the collection of Dr. Grindrod, is named by the author Trichotaster pluniformis.

I.—Gems from Private Collections, No. 1

The beautiful fossil Star-fish, which forms the subject of this paper, and is represented of the natural size upon the accompanying Plate VIII., is from the cabinet of Mr. Henry Johnson, of Dudley, the Honorary Secretary of the South Staffordshire and East Worcestershire Institute of Mining Engineers. It was obtained some years since in the shale between the Wenlock and Aymestry Limestones (probably Lower Ludlow shale), at Sedgley, near Dudley.

I.—On a Newly-discovered Long-eyed Calymene from the Wenlock Limestone, Dudley

It is more than a century since the “Dudley Locust,” or ‘Trilobite,’ was first figured and described, 1 and the locality where it it is found, is rendered famous by the researchs and writings of Sedgwick, Phillips, Forbes, Murchison, Salter, Davidson, and a host of other geologists and palæontologists, who have been attracted thither at various times by the grand geological features of the district or by the matchless beauty and endless diversity of its well-preserved organic remains.

On the Discovery of a New Genus of Cirripedia in the Wenlock Limestone and Shale of Dudley

T he genus Chiton of Linnæus (established in 1758) is remarkable among the Mollusca from the aberrant form of its shelly covering. Dr. Woodward, in his ‘Manual of the Mollusca’ (p. 156), thus describes it:— “The shell is composed of eight transverse imbricating plates, lodged in a coriaceous mantle which forms an expanded margin around the body. “The first seven plates have posterior apices, the eighth has its apex nearly in front. “The six middle plates are each divided by lines of sculpturing into a dorsal and two lateral areas. “All are inserted into the mantle of the animal by processes (apophyses) from their front margins.” I may add that these plates are always unilinear, and that the two sides are symmetrical, such an instance as a Chiton with unsymmetrical or bilineal rows of plates being unknown (see Plate XIV. fig. 6). More than 200 species are known, occurring in all climates throughout the world, from low water to 25 fathoms; and it is interesting to find that upwards of forty species of Chitons are recorded by palæontologists in a fossil state, extending back in time to the epoch of the Lower Silurian. During the past month I have had my attention drawn by Messrs. E. J. Hollier and Charles Ketley to the two species of fossil Chitons which were described and figured by M. L. de Koninck (‘Bulletins de l'Académie Royale des Sciences, &c., de Belique,’ 26 me année, 2 me sér. t. iii. 1857*, p. 199, pl. 1. fig. 2), and

Note on the Fossil found in the Worcester and Hereford Railway Cuttings

The tunnel through the hill (near Malvern) has given me a better idea of the Woolhope beds than I ever had before. The quantity of fossils is extraordinary. Our own collector, Mr. Gibbs, of the Geological Survey, Dr. B. B. Grindrod of Malvern, and other friends have obtained a great many, and in the most perfect state of preservation. Of Corals there are only a few—the ordinary Wenlock species (for the Woolhope limestone is nothing else than a lower Wenlock rock). Of Cystideœ the little Echinoencrinus armatus is frequent enough, Trilobites are abundant. Illœnus Barriensis attained its full size here. The strawberry-headed Trilobites ( Encrinurus ) are in great perfection, also Cheirurus, Sphœrexochus mirus with its globular jiead, Acidaspis, Lichas , and four species of Phacops , including P. Downingiœ , the well-known Wenlock and Ludlow form. The most common shells are, of course, Brachiopoda , as in all these muddy sediments. Lingula Lewisii and L. Symondsi (MS.) are plentiful; Atrypa , four species of Strophomena (of large size), Discina, Crania , three species of Spirifer , four species of Orthis , six or seven of Rhynchonella , just as in the Wenlock limestone: Pentamerus linguifer and P. rotundus are the most plentiful of all; the latter we have hitherto thought a rare species. Of the other bivalve shells there are Cardiola, Mytilus, Pterinea, Avicula , and Nucula . Aviculce, of two or three species, are the most common.

XV.—Observations on two new species of Chiton from the Upper Silurian ‘Wenlock Limestone’ of Dudley

XV.—<i>Observations on two new species of</i> Chiton <i>from the Upper Silurian ‘Wenlock Limestone’ of Dudley</i>

On the “Caradoc Sandstone” of Shropshire

Summary The conclusions to be drawn from the foregoing data may be thus shortly stated. The rocks east of the Longmynd hitherto known as Caradoc sandstone are now divided into two groups. The lowest and greatest portion is equivalent to the middle and upper portions of the Llandeilo and Bala rocks, and were accumulated in the following order:— 1. Fine shales, with small Trilobites ( Olenus, Asaphus, Agnostus ) and shells, deposited in deep water (most probably the equivalents of the Black Shales, Malvern). Elevation of Land, or Shallowing of Sea. 2. Coarse calcareous grits and conglomerate; a littoral or shallow water deposit. 3,4. Sandstones, with occasional pebbles, laminated in the upper parts, and in some localities northwards with many beds of shale. finer deposit than the last, and indicating a greater depth of water. Fossils exactly those of Bala. 5. Thin-bedded arenaceous shales, with fewer fossils, but of the same species; Trinucleus concentricus very abundant. A still greater depth of water is here indicated. (The higher part of the Llandeilo or Bala series.) Evidence of upheaval and partial dislocation. 6. A coarse deposit (unconformable on Nos. 1 to 5) in the immediate neighbourhood of the Longmynds, and derived from them (in part deep water around steep land, Forbes ). A great change in the organic remains. The characteristic Llandeilo and Bala fossils have given place to a mixed series, including several species found in the Upper Llandeilo flags, but with many others more characteristic of the Wenlock limestone. 7. Finer sandstones, with much shale and great abundance of Pentameri , and other Brachiopoda. Land gradually sinking ( Ramsay , Geol. Journ. vol. ix. p. 175). Fossils chiefly Upper Silurian. 8, 9. Grey and greenish shales, very fine sediment: deep water. Trilobites, Graptolites, and Cephalopods abundant. Fossils all Upper Silurian.

Observations on Dudley Trilobites

T he genus Lichas has received little attention from British palæontologists, and even Burmeister was compelled to omit any notice of it from the want of characteristic specimens. In the hope of being enabled to contribute some materials towards a more perfect knowledge of the genus, I am induced to offer to the Society a notice of several undescribed species which have recently been found in the Wenlock limestone of Dudley.

On the Basaltic Formation of the South Staffordshire Coal Field

The South Staffordshire coal field consists of a long wedge-shaped mass of the carboniferous formation, lying immediately upon the Wenlock limestone and shale of the Silurian system, which has been thrust up through the permian and new red sandstone deposits. From its base, near Hales Owen, where it is about six miles wide, and which there gradually rises from underneath the permian and new red sandstone, it extends in a direction N.N.E. towards the town of Rugeley, a distance of about twenty-three miles, bounded on its two sides by two large faults, which converge towards each other until they meet near that town. These faults bring this wedge-shaped mass of Wenlock limestone and shales, and coal measures, into immediate and abrupt contact with the permian and new red sandstone, on its east and west sides; but this is somewhat interrupted on the eastern side, near Walsall, by the elevation to the surface of the Wenlock shale and limestone. The effect of the elevatory force which raised this great mass, was to bring the Wenlock shale and limestone, and the coal measures, which were previously covered with the permian and new red sandstone, estimated by Mr. Jukes to be about 3,000 feet thick, from its former low level to such a height that the Wenlock limestone, which lay at the bottom of all, now forms the highest land in the district, and the coal measures are on a level with the surface of the new red sandstone. Thus the whole of ...

XXXIII.—On the Geology of Coalbrook Dale.

Illustrations.—Pl. XXXV. to XLI. Introduction. In the following pages two memoirs are embodied. One of them, read before the Society in February 1834, gave a short account of some of the principal faults and disturbances of the Coalbrook Dale coal-field; the other, read April 1836, described the several formations comprised in that district, as well as certain phænomena exhibited by the coal-measures, and not noticed in the former communication. Before I proceed, it is necessary to observe, that prior to the researches of Mr. Murchison into the formations between the carboniferous rocks and the slates of Wales, the examination, of the Coalbrook Dale district was attended with very considerable difficulties. A few of the rocks, which crop out against the flanks of the Wrekin, had been ascertained to be counterparts of others; but their order of superposition and relative antiquity had not been determined. Mr. Murchison’s labours, however, have removed these difficulties, by showing, that the thin zones of gray and liver-coloured sandstones, shales, and limestones, which overlie the limestone at Wenlock, and underlie the coal-measures at Madeley, Broseley, &c., are referable to the Ludlow rocks, the first formation beneath the old red sandstone, and constituting, with the Wenlock limestone and shale, the upper Silurian group; and that the shelly sandstone at Morrell’s Wood, as well as the quartzose grit, and dark-coloured flags at the base of the Wrekin, belong to the Caradoc sandstone, or lower Silurian rocks. The deposits just noticed form, in this district, the terminating points