Millstone Grit Research Articles

THE CARBONIFEROUS SEQUENCE OF THE CRAVEN LOWLANDS SOUTH OF THE REEF LIMESTONES OF CRACOE

I.—INTRODUCTION. The Craven Lowlands, bounded to the north-west by the Millstone Grit of the Bowland Fells and to the south-east by that of the Pendle Range and the Mid-Pennine Moors of Yorkshire, is an area of Lower Carboniferous built of a series of E.N.E.—W.S.W. folds, the most noticeable of which are the Clitheroe-Skipton and Slaidburn-Cracoe anticlines.* The north-eastern end of the Slaidburn-Cracoe anticline is crossed by the Craven Faults; the North Craven Fault separates the reef limestone of Cracoe from the more northern facies; the Middle Craven Fault divides the reef limestone of Elbolton and Thorpe Kail from that of Swinden and Butterhaw, while the South Craven Fault splits up into two faults which pass through Winterburn and Gargrave respectively and divide the area under consideration in this paper. This north-eastern part of the anticline was called the Eshton-Hetton anticline by Dr. Wilmore.14* It includes the Cracoe knoll area, where the anticline degenerates into a series of smaller folds of which one is the anticline of Swinden knoll, one the main axis of the Elbolton group of knolls, and one of which is continued across the North Craven Fault and forms the anticline between Dibbles Bridge and Greenhow.3 The area dealt with in this paper is that part of the Slaidburn-Cracoe anticline which is immediately south-west of the Cracoe knoll area and between the Millstone Grit of Threshfield Moor and that of Embsay Moor and Rylstone Fells (see map, p. 415). The investigation of the geology of this ...

The Base of the “Millstone Grit” Near Haverfordwest

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On the Fossil Flora of the Bristol and Somerset Coalfield

Summary(1) 510 plants are recorded from various localities in the coalfield, fossils having been collected from several new localities.(2) Fossil-plants are noted for the first time from the upper beds of the “Millstone Grit” of this district.(3) Two new species of Sigillaria are described and figured.(4) The known flora of the coalfield has been increased. Of the plants recorded—6 species have not been recorded previously from Britain.62 species have not been recorded previously from the coalfield, and290 species have not been recorded previously from various localities in the coalfield.Many of the species which have been previously recorded are here referred for the first time to definite horizons.(5) The known vertical distribution of 38 species is extended to the Staffordian Series.

THE NATURE OF THE JUNCTION BETWEEN THE LOWER CARBONIFEROUS AND THE MILLSTONE GRIT OF NORTH-WEST YORKSHIRE.

The greater part of North-West Yorkshire is composed of almost horizontal Lower Carboniferous rocks capped by Millstone Grit. The Lower Carboniferous, divided into Great Scar Limestone and Yoredale Series, is exposed over most of this area in the dales eroded by the Yorkshire rivers, and the Millstone Grit occurs as isolated outliers on the hills dividing one dale from the other. In the east, however, the general easterly dip of both Millstone Grit and Lower Carboniferous results in the occurrence of the Millstone Grit at a lower level, where it forms extensive tracts of moorland. The area under discussion includes the upper part of Swaledale, Wensleydale and Arkengarthdale in the north, and Semerdale, Bishopdale, Upper Coverdale and Wharfedale as far as Grassington in the south. The geology of part of the area has been described in the Mallerstang and Ingle-borough Memoirs (Sheet Memoirs 97 N.W. and 97 S.W.), while the entire area is geologically mapped on the One Inch Sheets 97 and 92 S.E. (Old Series). The mapping by the members of the Geological Survey was largely lithological. The rocks are exposed in a series of stream sections, and the intermediate country is usually covered with drift or scree detritus. As the lithology of the Lower Carboniferous gradually changes from north to south from a series of sandstones, shales and limestones to a facies composed of limestone only, the relation of the Lower Carboniferous and the Millstone Grit is not brought out. The work of Professor Garwood and Miss Goodyear ...

V. The Carboniferous Strata below the Top Hosie Limestone in North Ayrshire

Introduction. The area with which this paper is concerned lies for the most part within the Ordnance Survey one-inch Sh. 22, Scotland, but references are made to adjoining portions of one-inch Shs. 30 and 23, which are situated respectively north and east of Sh. 22. The resurvey of these sheets by the Geological Survey has been in progress for a number of years, and that of Sh. 22, in which the writer has been engaged, has now been completed. A general account is given of the geology of the older Carboniferous strata up to the top of the Lower Limestone Group. Particularly, attention is paid to an overlap of the limestone-bearing strata that succeed the Calciferous Sandstone lavas. This overlap and unconformity was recognised during the original survey fifty years ago. In more recent years, the detailed stratigraphy of the limestone-bearing strata below the Top Hosie Limestone has been worked out by many investigators from surface information and data supplied by bores. Many of the results obtained have been already published in the Society’s Transactions and in Geological Survey Memoirs. In the present paper use is freely made of these sources of information. The writer has also had the opportunity of visiting districts surveyed by other members of the staff. A statement of his main results has been contributed to the “Summary of Progress for 1923” ( Mem. Geol. Surv. ). The following groups of strata occur within the area:— Coal Measures. Millstone Grit. Carboniferous Limestone Series. {Upper Limestone Group. Limestone-Coal Group. This 250-word extract was created in the absence of an abstract The writer wishes to acknowledge with many thanks his indebtedness to Mr. E. M. Anderson for his collaboration in the field, in the Galston district, and to Mr. E. B. Bailey for much help received during the progress of the work.

THE MILLSTONE GRIT AND YOREDALE ROCKS OF NIDDERDALE.

I. INTRODUCTION. Nidderdale lies almost entirely in the Millstone Grit country, but in the upper reaches, limestone appears in several small inliers, which are named on the accompanying map. (Plate xix.) At Limley a considerable thickness of massive limestone is exposed, elsewhere limestones and interbedded shales are seen in the bottom of the valley. The limestones have long been known to belong to some part of the Yoredale sequence, but their precise horizon has not previously been ascertained. The Millstone Grit consists of the usual variable series of grits, sandstones, shales, and thin coal seams, and extends from the Basement or Bearing Grit of Grassington Moor to the Brimham Grits at the top of the series, the total thickness being about 1,650 feet. The Brimham Grits, formerly considered to be part of the Third Grit Series, have been correlated by Mr. W. S. Bisat with the Kinderscout Grit and Shale Grit of Derbyshire. In this area, therefore, attention is confined to the lower part of the Grit sequence; the beds above the Kinderscout Grit, which occur in the adjoining parts of Yorkshire and Lancashire, being absent. Two marine horizons : the Colsterdale Marine Band (the “Tesselated Limestone.” of the Geological Survey), and the Cayton Gill Beds, are known; and were mapped by the Survey over a wide area. In the autumn of 1922, Mr. Bisat directed the writer’s attention to the important section which would be exposed in the excavations for the dam of the new reservoir at Scar House.

“Farey's Grit.”

The present paper deals briefly with the historical aspect of the boundary between the Pendleside Series and the Millstone Grit Series in the Roches district and surrounding country of North Staffordshire some 4 miles north-east of Leek; and particularly with the term “ Farey's Grit ”. It seems to me probable that the difficulties as to limitation and classification of these divisions of the Carboniferous System are by no means limited to the small area with which I am familiar. The substance of this paper is derived from the works listed at the end, and has formed itself as a result of attempts to map the rocks in detail.

The Avonian of the Tytherington-Tortworth-Wickwar Ridge, Gloucestershire

The Author describes and maps, in terms of Vaughan's system of zonal classification, the northern portion of the horseshoe-shaped wooded ridge of Avonian rocks which partly surrounds the synclinal basin of the Bristol Coalfield lying north-east of Bristol. The area described links together the researches of two former papers, and completes the Avonian zonal map of the horseshoe ridge. The chief zonal characteristics may be summarized as follows:— Cleistopora Zone.—Lithologically the zone consists of shales. grits, and thinly-bedded muddy limestones, with the usual fossils. The Bryozoa Bed (α) has been recognized, and the zonal fossil is unusually abundant in the Tytherington-Grovesend railway section. Zaphrentis Zone.—Limestones of the ‘Petit Granit’ type, with intervening shales in Z 1 , form the major part of the sequence. At the base of Z 1 in the Tytherington-Grovesend railway section is an interesting band of oolite. No chert has been found. Zaphrentids are very abundant, and the ‘Z 2 Fish-Bed’ occurs in the northern part of the area. Horizon γ cannot be differentiated, owing to the absence of Caninia immediately above the konincki subzone. Syringothyris Zone.—The following sequence occurs in ascending order:— (1) Thickly-bedded, nearly unfossiliferous. blue-grey dolomites ( laminosa dolomites), apparently formed by the dolomitization of crinoidal limestones. (2) A series of fossiliferous crinoidal limestones (Sub-Oolite Bed): non-oolitic in the lower, but oolitic in the upper portions. (3) A thick bed of current-bedded white oolite ( Caninia Oolite). This was probably immediately followed by a short period of subaërial denudation. (4) Unfossiliferous thinly-bedded dolomites, with subordinate shales ( Caninia Dolomites). Series (2) and (4) a.re considerably thicker than their eqnivalents in the Avon Section. Seminula Zone.—The zone consists of massive limestones, including examples of , Seminula Pisolite, china-stones, and Seminula Oolites merging into sandstones and conglomerates of a ‘Millstone Grit’ phase of deposition. A calcareous sandstone (Firestone) occurs near the base of S2 (formerly described from the top of Sl). A calcareous development of the Dibunophyllum Zone is absent in the area described. It is thus established, from the evidence of previous writers and that set forth in the present paI)er, that during Avonian times there was a progressive movement of the northern shore-line of Vaughan's ‘ South-Western Channel ’ in a southerly direction. This movement is registered by noting the level in tile Avonian sequence at which ‘ Millstone Grit’ conditions were established. The maximum thickness of the calcareous Avonian beds is only 1280 feet, as compared with 2540 feet in the Avon section. The Tytherington-Grovesend railway provides a complete section of the Avonian rocks of the area.

Further Observations on the Volcanic Geology of East Fife

To the old volcanoes of East Fife Sir Archibald Geikie assigned a Permian age. In the course of a characteristically able series of investigations he discerned that on the shore at Lundin Links one vent had penetrated some of the highest members of the Scottish Coal Measures, whereas at Kennoway another could be seen to have risen through the Millstone Grit. There further appeared to be a general similarity in the lithologic and petrographic characters of the materials of the entire group, thus linking them together, and they seemed to have taken birth after the inception of the tectonic features of the area. Only one simple conclusion emerged from a consideration of these facts, namely, that the vents must be referable to some period of post-Carboniferous time. In support of that opinion he pointed especially to the Largo district, where he thought he could detect a sheet of fragmental volcanic material resting with a distinct unconformability upon the folded and denuded Carboniferous strata, which supposition, of course, could it be confirmed, would render further discussion upon the matter unnecessary. But in the East Fife Memoir it is stated that the sections which might be expected to furnish critical evidence are not clear.

ON THE RHYTHMIC SUCCESSION OF THE YOREDALE SERIES IN WENSLEYDALE

The alternations of sandstones, shales and limestones which occur between the Great Scar Limestone and the Millstone Grit in the West Riding of Yorkshire form a distinct facies of the upper part of the Lower Carboniferous, and have long been known as the Yoredale Series. This name was given to them by Phillips *, who first described them in detail, and took as his type section that so well exposed in Wensleydale. He chose, to use his own words, “as a general standard of reference for this complex series of rocks that district where this complexity is greatest. The upper end of Wensleydale was, therefore, adopted.” Later he records the fact that other sections were very satisfactorily in accordance with the Wensleydale section and “ justifies the use of that as a common standard of reference.” Phillips regarded the shale which lies immediately above the Gayle Limestone as marking a distinct change in the physical conditions under which the beds were accumulating in this area, and he, therefore, commenced the Yoredale Series with this shale. The change, however, from normal limestone to Yoredale conditions occurs before this. Shales, notably the Gayle shale, occur near the top of the massive limestone, together with algal horizons, which are very characteristic of Yoredale conditions of sedimentation. One such horizon, in particular occurs 49ft. below the top of the Great Scar Limestone, and this horizon, the Girvanella Bed, is taken, for the purposes of this paper, as the base of the Yoredale Series. A …

THE CARBONIFEROUS GONIATITES OF THE NORTH OF ENGLAND AND THEIR ZONES

Stratigraphy. The Carboniferous strata consist, except near the shore lines of that age, of two clearly marked divisions: a lower division, consisting mainly of clear water deposits (Mountain Limestone) and an upper division (Millstone Grit and Coal Measures), almost entirely composed of beds of detrital origin. When, however, the sequence is examined more closely it is seen that the details of the lithological succession vary greatly in different areas, and hence arises doubt and hesitation in correlating widely separated areas. The work of zoning the lower (Mountain Limestone) division by means of its contained fossils made great strides in Britain in the opening decade of the century, mainly through the researches of the late Dr. A. Vaughan. The main zonal divisions of the Lower Carboniferous propounded by him and based on the coral sequence, are now generally accepted as a basis for the correlation of widely separated deposits in North West Europe. His views on the succession exposed in the North of England formed Dr. Vaughan’s last paper, published in the Proceedings of this Society for 1916 (Vol. XIX, Part II, p. 41 et seq .). In Britain and Western Europe generally, the oncoming of the coarse detrital deposits of Upper Carboniferous time drove out the coral fauna, and this group is, therefore, not available as a time-index for the Upper Carboniferous rocks. We are, therefore, compelled to turn to other groups more or less abundantly preserved in these beds, namely the lamellibranchs and goniatites. The researches of the late Dr. …

The Unconformity between the Millstone Grit and the Carboniferous Limestone at Ifton, Mon.

The object of the present communication is to place on record a section, apparently unique, in which the unconformity between the Millstone Grit and Carboniferous Limestone that exists in parts of South Wales and Monmouthshire is clearly displayed. The exposure was first examined at the suggestion of the brilliant worker who threw so much light on Lower Carboniferous problems, the late Dr. Vaughan. The writer had explained1 the attenuation of the Carboniferous Limestone Series in the Newport (Mon.) district as due to unconformable overstep by the Millstone Grit, similar to an overstep at this horizon that had already been observed near Haverfordwest, at the other end of the South Wales basin, by Professor O. T. Jones.1 The value of the Ifton section in demonstrating that this overstep was widespread was recognized, and photographs, two of which are here reproduced, were secured by H.M. Geological Survey. Since then the unconformity at the eastern end of the South Wales coalfield has been confirmed by the detailed examination of a large area by Mr. F. Dixey and Dr. T. F. Sibly,2 and has been found by the writer, in the course of work not yet published, to reach its greatest known extent in the Abergavenny district. Nevertheless, it seems desirable to describe the Ifton section because it is the clearest exposure known, in the whole of the South-West Province, of the unconformity between the Carboniferous Limestone and the Millstone Grit, and also on account of the remarkable inter-relations of the two formations which it reveals.

XVII. The Occurrence of Iron Ore in Millstone Grit Lava, Ayrshire

In 1895 Mr. John Smith (Trans. Geol. Soc., Glasgow, 10, 133, 1895), contributed a paper to this Society, describing a deposit of volcanic ash in Ayrshire, containing bands of ironstone. During the following twenty years there was practically nothing done in the way of further exploration of these deposits until the urgent demand for a supply of ironstone in this country led Mr. G. V. Wilson, of the Geological Survey Office, Edinburgh, to make a careful inspection of this horizon. The volcanic zone referred to lies immediately below the base of the Coal Measures Series, and is now considered to be of Millstone Grit age. The average section of Millstone Grit, as exposed in North Ayrshire, is as follows:— Bauxitic clay, \- - -| - - 3 to 9 feet. Series of lava flows with interbedded sediments, \- - -| - - 70 to 180 ’’ Monkcastle fireclay, \- - -| - 0 to 20 ’’ Sandstone, \- - -| \- - -| 0 to 20 ’’ Sandy fireclays, and blaes with marine fossils, and occasionally thin limestones, \- - -| - - 0 to 20 ’’ The lava flows are often much decomposed and altered by processes similar in many ways to lateritization, whereby their iron contents has been proportionately increased by the abstraction of silica and alumina. This type of alteration is most common near the top of the series, although in a section at Glenburn it can be observed that the basal flow is also affected. The This 250-word extract was created in the absence of an abstract

The Petrography of the Millstone Grit of Yorkshire

The term ‘Millstone Grit’ is applied to a series of beds which attain a thickness of 5500 feet in Lancashire, consisting of conglomerates, grits, sandstones, and shales with occasional thin impure limestones and beds of chert. It occupies a position in the geological sequence between the Yoredale or Pendleside Group and the Coal Measures. For the purposes of this investigation the base of the Millstone Grit in West and North-West Yorkshire has been taken at the base of the Ingleborough Grit, following the precedent of the Geological Survey as pointed out in the Memoir on the Ingleborough District, 1890, pp. 74–75. Since this is a coarse grit, easily traceable on account of its lithological characters and the bold escarpments to which it gives rise, it forms a good datum-line. The top of the series has been taken at the top of the Hough liock, where it can be seen to be overlain by the Lower Coal Measures, as at Whitehall Quarries, Horsforth, near Leeds. However, as no questions of correlation are involved in this work, the exact delimitations of the various beds is a matter of minor importance. The Millstone Grit Series covers an area in Yorkshire alone of no less than 840 square miles, and is important physiographically, as it forms the capping of most of the hills of the Pennine Chain, such as Mickle Fell. Whernsicle, Ingleborough, Penygent, etc., and by its presence there preserves the more easily denuded strata below from a more rapid destruction. Economically the

In Memoriam: William Simpson

(1859—1915.) The death of William Simpson, of Catteral Hall, Settle, was a serious loss to the Society of which he was so active a member, as well as to his numerous personal and geological friends. Born on December 18th, 1859, Mr. Simpson was son of the late Thomas Simpson, of Halifax, and was for many years associated with the firm of Simpson & Sons, Ltd., cabinet makers, of Halifax and Blackburn, a business which had been established in the early days of the nineteenth century by his grandfather, John Simpson, a native of Rudston, near Bridlington. Beside acting as managing director of this business, Mr. Simpson was a director of the Calder and Hebble Navigation Company, and of Messrs. J. W. & C. Ward, Ltd., textile manufacturers. Until middle life he lived in Halifax, and in his youth came under the influence of the local group of naturalists who have left so strong a mark in Yorkshire scientific history. For many years he took a prominent part in the affairs of the Halifax Scientific Society, which body he served as president, and to which he gave several lectures, his special interest being the local geology of the Millstone Grit. He was a member of the Yorkshire Naturalists’ Union, and served for some years on the committee for observing and recording glacial boulders. He studied glaciology in Switzerland and Norway, and in some of his addresses turned the knowledge thus acquired to good account in the interpretation of the glacial …

The Carboniferous Limestone bordering the Leicestershire Coalfield

I. Introduction. The area containing eight inliers of Lower Carboniferous rocks with which this paper deals is situated north and east of Ashby-de-la-Zouch. These inliers of Avonian rocks lie within a radius of 6 miles from Ashby-de-la-Zouch, and the area forms a quadrant with the line Ashby-Ticknall as the south-to-north radius, and the line from Ashby passing through Thringstone as the west-to-east radius. The westernmost inliers, Ticknall and Calke, are in Derbyshire, as is also part of the Dimminsdale inlier. The Heath End stream which flows through the last inlier is there the county boundary. The eastern side of Dimminsdale and all of the remaining inliers, from Breedon to Grace Dieu inclusive, are situated in Leicestershire. The Carboniferous Limestone of the area has been mentioned but briefly in the Memoirs of the Geological Survey, and the relations of the Lower Carboniferous to the Millstone Grit have not been definitely stated. The original survey of the district was made by Edward Hull, and his results were published in 1860. 1 His map shows a ninth Carboniferous Limestone inlier situated north of Breedon-on-the-Hill, and south-east of Melbourne, but no description of it is given in the Memoir, and it is not shown in maps published more recently by the Geological Survey. In the same Memoir (1860) a list of fossils obtained from Breedon and Breedon Cloud is given; but Hull considered the two Breedons to be alike stratigraphically, and the names of the fossils from the two places were put together

Societies and Academies

LONDON. Geological Society, June 28.—Dr. Alfred Harker, president, in the chair.-Dr. A. Smith Woodward: A new species of Edestus from the Upper Carboniferous of Yorkshire; with a geological appendix bv J. Pringle. The fossil confirms the interpretation of Edestus as a row of symphysial teeth of an Elasmobranch fish. The row of eight bilaterally symmetrical teeth, fused together, occurs at the tapering end of a pair of calcified cartilages, which evidently represent a jaw. An imperfect detached tooth probably belongs to an opposing row. The teeth are large compared with their base, and the serrated edges have been worn during life. Small Orodont teeth of the form named Campo-dus are scattered in the shale near the jaw. Markings on the Edestus teeth themselves suggest that they have been derived from the Campodus type of tooth. The specimen was obtained from shale below the Rough Rock, in the upper part of the Millstone Grit, at Brockholes, near Huddersfield.-A. Holmes: The Tertiary volcanic rocks of Mozambique. With the exception of a coastal belt of Cretaceous and Tertiary sediments, flanked on the west by later Tertiary volcanic rocks, the territory consists of a complex of gneisses and other foliated rocks, intruded upon by granites belonging to at least two different periods. From Fernao Vellosa Harbour to Mokambo Bay the junction of the sedimentary formations with the crystalline complex is faulted, and the volcanic rocks are distributed on each side of the fault. The lavas are of post-Oligocene age, and are the result of fissure-eruptions, the feeding channels being exposed as small dykes that penetrate the underlying rocks. The prevailing lavas are amygdaloidal basalts. An andesite dyke of later date occurs near the Monapo River. In the north, near the Sanhuti River, picrite-basalt, basalt, phonolite, and solvsbergite have been found, and related lavas occurring elsewhere in the area are tephritic pumice and segirine-trachyte. The “alkali” series can be closely matched by the lavas of Abyssinia, British East Africa, Reunion, and Tene-riffe. The amygdaloidal basalts of the “calc-alkali” series are similar to those of the Deccan, Arabia, and East Africa, and also to those (of late Karroo age) occurring in South Africa and Central Africa. Each of the series was probably evolved by a process of differentiation acting on a parent magma. From1 the composition of the amygdale minerals it is deduced that the parent magma of the “alkali” series was rich in carbon dioxide and under-saturated in silica; whereas that of the “calc-alkali” series was rich in water and over-saturated in silica. The radio-activity of the lavas indicates that the depth from which the parent magma came was probably between thirty-three and forty-four miles from the earth's surface.

Note on the Well-Section at Rock Mills and the Fauna associated with Edestus

The well at Rock Mills (Messrs. Joseph Sykes & Co.) is situated in the mill-grounds in the valley of the River Hohne at Brockholes, about 4 miles south of Huddersfield. According to the Geologiqal Survey-map (Quarter-Sheet 88 S.E.), the alluvimn in the valley at this point rests on shales which underlie the Rough Rock, the uppermost member of the Millstone Grit. The shales appear to vary considerably in thickness in this district. Green states that 100 feet of shales are present between the Rough Rock and Grit A about Holmfirth, which lies 2 miles south of Brockholes; while on Holestone Moor, west of Huddersfield, he estimates that thev are 200 feet thick between the same horizons. Spencer has shown that in the district embraced in the next sheet to the north (Quarter-Sheet 88 N.E.) the shales contain a marine fauna; and the discovery of Edestus should stimulate the efforts of the local geologists to further work on this horizon. During the excavation of the well no record of the various strata passed through was made by the sinkers; but it appears, from notes supplied by Mr. J. R. Simpson, of Banks, Honley, that the rocks were mainly shales, with some thin beds of sandstone. At the depth of 120 feet the specimen of Edestus was obtained by Mr. H. H. Freer in a bed of rock—rather friable shale,—which also contained numerous fragments of marine shells. Among the specimens the following have been identified:— Posidoniella lœvis (Brown), Gastrioceras sp., Glyphioceras reticulatum (Phill.)

On a New Species of Edestus from the Upper Carboniferous of Yorkshire

The remarkable Upper Palæozoic fossil Edestus has already been proved to represent a row of symphysial teeth of an Elasmobranch fish, but it has hitherto been found only once in direct association with portions of jaws. A second specimen, still more instructive, has now been obtained by the Geological Survey from the upper part of the Millstone Grit at Brockholes, near Huddersfield, and I am indebted to Dr. Aubrey Strahan and Dr. F. L. Kitchin for the opportunity of studying it. The circumstances of its discovery are described in the Appendix by Mr. John Pringle. The new fossil, shown of two-thirds the natural size in Pl I, fig. 1, displays a single example of Edestus , with a detached dental crown and another fragment of the same form, near the tapering ends of a symmetrical pair of cartilages ( c ) which evidently represent a jaw. Whether they are upper or lower is uncertain, on account of the shortness of the portions preserved; but, as the anterior ends suddenly begin to taper and eventually become very slender, they are probably the pterygo-quadrates of the upper jaw. The cartilage is well calcified in very small tesseræ, and, as shown both by the portions of jaws themselves and by remains in front of the fossil, the calcification penetrates more deeply than is usual in recent Elasmobranchs. The best-preserved outer surface of the cartilage, on the side of the specimen not shown in the figure, is slightly marked with scattered fine pittings, such as have already

Aulina rotiformis , gen. et sp. nov., Phillipsastræa hennahi (Lonsdale), and Orionastræa , gen. nov.

I. Introduction Phillipsastræa is a genus of Devonian Corals possessing certain well-marked characters. The genus Orionastræa has been established to include certain Carboniferous species very closely related to Lithostrotion , but which have been regarded by many writers as congeneric with those of Phillipsastræa. O. phillipsi (McCoy) is commonly known as Ph. radiata (Martin). Aulina is a new genus, found at the horizon of the Millstone Grit. One species only has been recognized: this has been confused hitherto with O. phillipsi , and hence recorded as Ph. radiata . I regard Phillipsastræa as the ancestor of Aulina , but do not consider that these are related to Orionastræa . All three genera, however, are colonial in habit, and possess a similar type of corallum: namely, that in which the individual corallites have lost their epitheca, and consequently are united by their dissepiments—a type of colony which may be termed ‘astræiform.’ The foregoing statements explain my reasons for including the history of the name Phillipsastræa and the description of its genotype in a communication primarily concerned with Carboniferous genera. I am deeply indebted to the late Prof. T. McKenny Hughes, to Dr. A. Smith Woodward, Dr. F. L. Kitchin, Dr. W. G. Lee, and Mr. Peter MacNair for the loan of material (including various type-specimens) preserved in the Sedgwick Museum, Cambridge, the British Museum (Natural History), the Museum of Practical Geology, the collection of the Geological Survey of Scotland, and the Glasgow Museum & Art Gallery; and to Mr. Charles Edmonds, Prof. E. J. Garwood, and