ALBERT

Description: The rocks of the Wirral Peninsula in Cheshire were originally described by John Cunningham in 1839, as three series, two moderately resistant to the east and the west, separated by a central region of soft sandstones and marls, dipping uniformly eastwards. G. H. Morton noted this in 1872, as a good description of the strata, ignoring faults, and pointed out the significance of the faulting. Since that date the faults have been mapped in great detail, and most of the structural features ascribed to them. G. H. Morton was particularly accurate with his mapping of faults both in Liverpool (1899), and in Storeton (G. H. Morton, 1883, and H. C. Beasley, 1914). The folding finds its first mention in the Geological Survey Memoir of 1923, two elongated synclines being mentioned, one from Heswall northwards and the other from Storeton to Prenton. The former is undoubtedly an important synclinal feature, but the latter is made up of two folds, a north to south anticline at Storeton, and an east to west syncline at Prenton. The only other records of folding in Wirral are by F. T. Maidwell in 1920 and by T. A. Jones in 1937, who mention an anticline at Ellesmere Port. This paper is therefore chiefly devoted to a description of the folding in the area.

Description: During an investigation of the upper part of the Sabi Valley made just before the war in company with my son, the late C. F. Mennell, two well-marked ring structures and indications of others were met with. Reference to these was made in a communication to the Rhodesia Scientific Association in 1938 before the investigation had been concluded or any of the rocks collected had been sliced. The suggestion was then made that they owed their remarkable features to the action of the enclosing granite on the limestone still forming their cores.

Description: Etruria Marls of N. Staffordshire, by W. O. Williamson, Geol. Mag., lxxxiii, 1946, p. 23, line 25, for quartz veins read quartz grains.

Description: In 1914 the British Museum (Natural History) acquired from William McPherson, the well-known collector, a few ostracoderms from the “Downtonian” of Lanarkshire. Among these were two specimens from Logan Water of an obviously new form, which, however, were so preserved that satisfactory identification by the methods then in use was not possible. They were tentatively labelled “allied to Lasanius” and are the “interesting though tantalizing new specimens” referred to by Smith Woodward (1921, p. 26) in his first Linnean Address. Nothing further was done with them for nearly twenty years, when the rearrangement of the collections again drew attention to these problematical fossils: and subsequent investigation has shown them to be of considerable importance.

Description: In a previous paper (Wright, 1935, p. 193) it was remarked that the crinoids of Coplow Knoll, Clitheroe, mainly consist of calices or thecae only and that specimens showing any part of the arms are extremely rare. In the paper cited, photographs were given of two specimens with arms, one being referred to a new species Cyathocrinus patulosus and the other to Pachylocrinus aff. longidactylus (Austin). Flexible crinoids belonging to the genus Euryocrinus, with part of the arm structure preserved, have also been recorded and a Poteriocrinid assigned to Pachylocrinus conicus (Phillips) (Wright, 1928, 1942). The latter species and P. aff. longidactylus mentioned above will probably have to be removed to another genus but it is not intended to discuss them at present. All these specimens were found at rather long intervals. I was therefore agreeably surprised on a recent visit to Coplow to find two fairly well-preserved crowns belonging to the genera Taxocrinus and Synbathocrinm and since the species represented by these specimens appear to differ from known forms they are now described in the present paper. An excellently preserved specimen of a species of Platycrinites was also found. This specimen shows a good part of the arm structure and although it is not possible to determine with certainty its specific identity the type of preservation exhibited by it is so rare at Coplow that it is here deemed worthy of being placed on record. Another specimen with arms, probably belonging to the same genus and found a few years ago is also recorded (Plate VII, fig. 1; Plate VIII, fig. 4).

Description: The most representative series of fossiliferous pebbles from the Birmingham district is that in the Evans Collection, which was acquired by the National Museum of Wales in 1937 and catalogued under the numbers 37.110 GR 1–316. For the loan of this collection I am indebted to Dr. F. J. North, and material for comparison from other collections was obtained from Dr. C. J. Stubblefield, Miss J. R. Harding, and Professor L. J. Wills, who has also corrected the typescript.

Description: In previous reconstructions of Gondwanaland the Falkland Islands have been placed in a position intermediate between the Cape Province and Northern Argentina. In the present paper it is suggested on structural, tectonic, and stratigraphical grounds that it would be preferable to position the Falkland Islands due east of the Eastern Province coast, thus completing the truncated Karroo Basin, the missing part of which has until now been suspected to be concealed beneath the ice-capped Queen Maud Land, Antarctica.

Description: The occurrence of large blocks of fossiliferous Cretaceous limestone among the Lower Cretaceous shales of the Central Range area of Trinidad, B.W.I., has been known for many years, and several different modes of origin have been advanced. A critical exposure which shows the field relationships between the shales and limestone blocks is described, from which it is concluded that the limestone blocks were derived from the contemporaneous breaking up of limestone reefs, and the inclusion of such blocks, together with fore-reef breccia, in the adjacent shale deposits.

Description: An attempt is made to correlate the concept of the fossil lineage with our knowledge of polytypic species. The influence of changing environmental conditions in the geological succession and the relationship between geographical and chronological sub-species is analysed on a theoretical basis. The fossil lineage is considered to be the resultant of combined evolutionary and environmental change. Phenotypic modifications in response to environmental conditions are discussed in relation to the study of variation in fossil communities.

Description: Study of the fauna from a newly discovered fossiliferous outcrop of the Cove Lower Marine Band in Thornton Burn, East Lothian, has led to the correlation of this horizon with the Redesdale Ironstone in Northumberland and has thereby demonstrated the first palaeontological link between the Upper Calciferous Sandstone in S.E. Scotland and the Lower Limestone Group in N.E. England. The collection of D1 fauna made from the Thornton Burn outcrop includes goniatites, brachiopods, lamellibranchs, and crinoids. The discovery of Beyrichoceratoides redesdalensis (Hind) gives the first definite indication of the presence of B zone in the Scottish Carboniferous. Faunal lists and descriptions of some of the more interesting species are included in this paper as well as descriptions of the crinoids collected which are given in the succeeding paper by James Wright.

Description: There are two alternative hypotheses regarding the relationship of the goniatite-bearing reef limestones to the coral-bearing “massif” limestones. One claims an unconformity between the reefs and bedded limestones, the other a lateral passage from a “massif facies” to “marginal facies”. Surface exposures are such that it is difficult to be convinced of either hypothesis. Details of underground exposures in natural cave systems and associated mine-workings show a clear transition between facies and no trace of unconformity.

Description: Specimens of Diversograptus are described which show conclusively how the two stipes arise from the sicula. This is also the first record of the genus occurring in Britain

Description: An intrusion-breccia filling a pipe is made of two parts, one of facetted quartzite fragments in a granophyric matrix, the other of calc-silicate-rock fragments in an appinitic matrix. The quartzite fragments are derived from a horizon at least 1,000 ft. below the breccia level, the calc-silicate-rock fragments are local. The mechanism of emplacement of the breccia is considered to be similar to that proposed by H. Cloos for the Swabian tuff-pipes. Neither the granophyre nor the appinite of the Kilkenny pipe is regarded as of magmatic origin.

Description: The crinoids collected by Mr. Hugh Wilson from the shales and ironstones of the Calciferous Sandstone Series in the Thornton Burn section in East Lothian are of special interest and are described herein. The list of species is as follows:—Talanterocrinus redesdalensis sp. nov.Blothrocrinus thorntonensis sp. nov.Anemetocrinus wilsoni sp. nov.Phanocrinus ardrossensis (Wright).Ureocrinus bockschii (Geinitz).Ureocrinus doliolus (Wright).

Description: The orientation of the optical indicatrix in synthetic and volcanic plagioclases differs from that in plutonic and metamorphic plagioclases, the former “optics” being commonly known as “high-temperature”, and the latter as “low-temperature”. The difference between the two series is most marked at the sodic end and decreases towards An70. The conclusion that the difference, though small, still persists in the range An70 to An100 is shown to be unwarranted on the evidence available. Grave doubt is thrown on the supposition that temperature is the controlling factor in determining the type of optics by Tuttle and Bowen's failure to synthesize low-temperature albite, even at low temperatures. It is known, however, that some low-temperature plagioclases (e.g. in albite-schists) have grown without the intervention of melt. The real antithesis may therefore be between plagioclases crystallized from melts, and those developed during the metamorphic reconstitution of rocks.From the fact that the plagioclase, quartz, and alkali feldspar of undoubted magmatic rocks such as quartz-porphyry and rhyolite are respectively systematically different from those of granite it is concluded that the latter is a metamorphic rock

Description: The ontogeny of Dalmanitina olini Temple (Upper Ordovician) is described on the basis of specimens from Scania and North Wales. The development is similar to that of D. socialis (Barrande), but good preservation has enabled some detailed changes in the cephalon to be followed. The protaspid and early post-protaspid stages bear an anterior pit in each axial furrow opposite the frontal lobe. The protaspid anterior glabellar furrow becomes joined to this pit by an oblique furrow, and forms with the latter a composite oblique furrow which develops into the adult anterior-glabellar furrow. This mode of development is considered probably to be common to all Phacopids: the significance of the anterior pits in this family is discussed. Preliminary observations are made on the growth-rates of various parts of the glabella, and the frontal lobe is found to grow in length (sag.) at a rate approximately equal to that of the rest of the glabella.

Description: The Malvern ridge consists of a series of Pre-Cambrian fault-blocks, which have been thrust upwards into their present positions through an overlying cover of Cambrian, Silurian, and Lower Old Red Sandstone sediments. The formation of the narrow. localized belt of folds which lie immediately to the west of the Malverns is the result of the displacement of the Pre-Cambrian basement blocks.

Description: Kinematic analysis of tension gashes in an exposure of the Moine Series indicates that the fractures resulted from a tectonic movement directed from north to south, unrelated to that responsible for the nearby Caledonian Moine Thrust.

Description: A group of eruptive rocks (weilburgites), widespread in the Lahn-region, is discussed in respect to its genesis. Their close relation to the keratophyres suggests a later mobilization of the keratophyric magma through the volatiles originating from the ascending diabasic magma (allopegmagenesis). In accordance with the character of the weilburgitic magma its ascent was accomplished by adaptation to the orogenic process (gradational ascent).Conditions of this kind might influence the magmatic evolution in several respects. They are intimately related to geological conditions. To them are referred the favouring of allopegmagenetic or even allomagmagenic rocks in Palaeozoic time, the possible difference in age between the beginning of ascent and the emplacement, the lack of correspondence in composition of some rocks with the composition of the originating magma. Thus, the question arises as to how far correlations may exist generally between the mode of magmatic evolution in space and time, the composition of the rocks and the geological age.

Description: In an attempt to dissect the granitization process in an area of regional metamorphism, it is suggested that granite is forcibly injected during strong compression, that the compressional wave passes upwards and outwards in advance of the magma, and that several changes take place before its arrival. Six stages in this process are recognized in the Cooma and Albury districts of N.S.W.: (1) Regional Metamorphism, (2) Superimposed Thermal Metamorphism, (3) Permeation without Magmatic Addition, (4) Addition from an Attenuated Magma, (5) Formation of a Potassic Wave-Front, and (6) Injection of the Magma as Concordant Intrusions. The conditions favouring granitization are discussed and the question of basic fronts is considered.

Description: An unusual appinitic sill intrudes and thermally alters regionally metamorphosed Dalradian sediments near Killin, Perthshire. The sill is composed of ultrabasic, basic, dioritic, and acid varieties, the last two being present only in minor quantity. The dioritic intrudes, and is chilled against the ultrabasic type. The appinitic varieties and contact Dalradian rocks are described together with their field relationships.

Description: A preliminary report is presented on the paragenesis of the Varuträsk pegmatite, situated about 10 km. from Skellefteå, in Sweden. Three main stages can be distinguished (a) An epimagmatic-pegmatitoid stage during which the primary zonal development of the pegmatite body into border zone, wall zone, intermediate zones, and core was accomplished; (b) a hydrothermal replacement stage, divisible into a high temperature phase with a Li-replacement unit and a Cs-replacement unit, and a lower temperature phase with a cleavelandite replacement unit and a feebly developed fluorite unit (c) a final stage of supergene alteration. The age of the pegmatite lies between 1650 and 1800 million years.

Description: Chromite-marbles from India and Finland are compared.

Description: The name hanléite is proposed for a magnesia-chrome garnet from Hanlé, Rupshu, Kashmir.

Description: The view is put forward that, as any subdivisions of an evolving plexus must be arbitrary, the existing binomial system of nomenclature should continue to be applied to morphological species in palaeontology, rather than be replaced by any other arbitrary system which could not be applied generally.

Description: The district of Strath Errick and Foyers, with which the investigation recorded here is concerned, occupies about 70 square miles southeast of Loch Ness, in Inverness-shire. The ground rises steeply from the loch to form a bordering ridge, beyond which it slopes more gently to Strath Errick. Further to the south-east, the hills rise to a height of 2,560 ft. in Beinn Bhuraich. The country is chiefly moor and hill grassland, with numerous exposures of rock; fairly extensive areas are under arable cultivation in Strath Errick. The district is drained by the Rivers Fechlin and Farigaig, both of which enter Loch Ness through deep gorges (Text-fig. 3).

Description: The new genus here proposed is based on nine specimens. All are more or less complete crowns. The best preserved example (Plate III, figs. 1, 2, 3, 5) was previously illustrated in Trans. Roy. Soc. Edin. as Synerocrinus incurvus (Trautschold) (Wright, 1939–1940, pl. xi, fig. 8). Later, the discovery of another well-preserved specimen caused some doubt about this interpretation and led to further cleaning and developing not only of the first mentioned specimen, but of others in my collection. Some of these were labelled as Synerocrinus incurvus (Trautschold) or the kindred species Amphicrinus scoticus Springer. From a study of all these specimens it is now evident that we are here dealing with a crinoid which differs in certain aspects from Synerocrinus or in fact from any other described Ichthyocrinid. Two specimens previously figured as Amphicrinus scoticus Springer (Wright, 1914, pl. xix, fig. 4, 1939–1940, pl. xi, fig. 2) are now here referred to the new genus.

Description: The grits and conglomerates in the Etruria Marls of North Staffordshire include types with a chamosite-rhombohedral carbonate cement containing interesting spherulitic and concentric structures. Manganese appears in this cement and in certain calcareous bands in the argillaceous fades of the Marls. The clastic fragments suggest derivation from Pre-Cambrian and Cambrian rocks. The heavy mineral suite resembles that listed by Fleet for similar horizons in the Midlands, but staurolite is recorded also.There is no new evidence bearing on Robertson’s hypothesis that basic igneous rocks of Carboniferous age have contributed to the formation of the Etruria Marls.

Description: In recent years the stratigraphical position of the Craighead Limestone, as assigned by Lapworth (1882) and by Peach and Home (1899), has been questioned by such competent geologists as Ulrich (1930), O. T.Jones (1935), and Cowper Reed (1935); any new evidence having a bearing on the age of the limestone is therefore worthy of being placed on record.

Description: The suggestion that the Skye amygdaloidal gabbro represents amygdaloidal basaltic lava in which the grain-size has been coarsened by recrystallization does not imply “an unusual type of metamorphism” as Bailey supposes. Whereas recent lava-flows are fine-grained, older flows, particularly pre-historic examples, commonly have a doleritic or gabbroic grain-Size. Bore-hole investigations in Yellowstone Park indicate that such increase in grain-size is a consequence of the long-continued through-passage of gases and water escaping to the surface. Bailey's own observation that amygdales within the Skye amygdaloidal gabbro “interrupt the form of the bigger feldspars” provides evidence that the bigger feldspars are younger than the amygdales, and that the rocks containing them have therefore recrystallized

Description: Certain amygdaloidal rocks in Skye have formerly been interpreted as lavas in which the matrix of the amygdales has been replaced by, or alternatively metamorphosed into, material such as one expects in intrusions. It is now claimed that the amygdales formed in intrusions in normal fashion

Description: Valley fill exposed in chalk pits at Barrington consists of two beds, which differ markedly in lithology and in the nature of the molluscan fauna contained in them. The lower bed is thought to predate the Boulder Clay, which caps the high ground, and the upper bed is considered to have been derived from the Boulder Clay. The lower bed, a chalk solifluxion, apparently spread into the Cam valley and covered the famous Hippopotamus bed. Both the Hippopotamus bed and the present depth of the Cam valley, therefore, probably predate the Boulder Clay.

Description: On Orval, in the Isle of Rhum, Tertiary plateau lavas directly overlie the granophyre of the ring-complex. Judd considered that the Orval basalts rest unconformably upon an old land surface cut in the granophyre; but on the supposed existence of veining and metamorphism later workers, in particular Geikie and Harker, concluded that the granophyre had intruded the volcanic pile. The author's re-examination of the Orval rocks supports Judd's early interpretation.

Description: The writer describes the relief forms and destructional processes occurring in a group of granite hills in Damaraland, South-West Africa. The hills are attributed to the dissection of a former erosion surface by rejuvenated streams. Drainage incision has followed longitudinal and diagonal joint lines, which control the orientation and sub-division of individual groups of granite domes. The destruction of granite masses by plating, or the unloading of Unweathered shells, produces the dome outline, whereas the development of vertical jointing leads to granite tors. Domes may be cleaved along transverse joints to form secondary domelets, or split longitudinally to form narrow whalebacks. The former are lowered by plating to flat dome forms the latter are reduced by marginal fracturing, here termed mural weathering. Further wastage is by slow granular disintegration on low granite outcrops.

Description: The conditions under which ptygmatic veins develop occur when the country-rock—as in a granitized area—is locally less competent or more yielding than quartzo-felspathic magma which may intrude it. Veins therefore which are being driven forward by pressure from behind, will buckle plastically if they encounter a resistance during injection, and a succession of such buckles will produce a typical ptygmatic vein. The amplitudes of the flexures so formed depend on the relative physical states of the vein and host-rock; so for any particular vein there is usually a more or less constant size for the tortuosities developed. The mechanism explains several features observed in examples of ptygmatic veins, and has been reproduced experimentally in the laboratory. The contortions are therefore not necessarily due to the deformation of the veins by post-injection flowage or tectonic movements of the country-rock.

Description: A Summary of the stratigraphy of the Coal Measures in the Kent Coalfield was given by H. G. Dines in 1933, accompanied by notes on the fossil flora by R. Crookall and on the fauna by C. J. Stubblefield. It was shown that the Coal Measures could be divided into a Lower or Shale Division, some 700 feet thick, consisting mainly of shales with some thick coals, and an Upper or Sandstone Division, about 2,100 feet thick, consisting mainly of sandstone with a few mostly impersistent coal seams, except in the highest part where again there are shales with coals (Dines, 1933, p. 22); the dividing line was taken at the base of a sandstone usually about 100 feet below the Millyard Seam. Recently the correlatable seams in the coalfield have been designated by means of numbers in downward succession and seams numbered 1–6 lie in the Sandstone Division, and numbers 7–14 in the Shale Division (Dines, 1945). R. Crookall regarded the Upper or Sandstone Division as representing the StafFordian and part of the Radstockian series, while the Shale Division he referred to the Yorkian (Text-fig. 1).

Description: Two specimens of Augitite (Nos. 64613–4) in the British Museum (Natural History) were collected during the voyage of H.M.S.Challenger (1872–6) and acquired by the Museum in February, 1890, through the Director of the Challenger Office, Dr. (later Sir John) Murray. The rock was briefly described by Renard,1 who noted the fibrous texture and unusual elongation of its pyroxene, as “related to the pyroxenites”.

Description: The determination of the true order of crystallization of minerals in a plutonic intrusion is not an easy matter, but a good deal of information on the subject may be obtained if such an intrusion shows a chilled edge or if there are dykes of corresponding composition. Fortunately, some of the Caledonian plutonic rocks of Western Scotland which we are about to consider do show chilled margins, and there is a series of dyke rocks, loosely termed porphyrites and quartz-porphyries, covering practically the whole range of composition for the rocks on the assumed liquid line of descent.1 It has been possible to study large collections of these housed in the Geological Department of Manchester University and in the Department of Mineralogy and Petrology, Cambridge.

Description: A small collection of fossils from the Upper Ordovician of Quarrel Hill, Girvan, made recently by Mr. James L. Begg, is remarkable for the number and character of the lamellibranchs, several of which appear to be new. Their affinities are chiefly with those of the Ordovician of the United States and are consequently of special interest.

Description: The evidence relating to the problems raised by the Arenaceous Formation of the Main Range Foothills may be summarized thus:—(i) The Foothills are built as a rule of predominantly arenaceous sediments; belts of quartzite-conglomerate occur and argillaceous types generally are interspersed with the coarser grained rocks.(ii) Lithological variations northwards and southwards along the strike of the Formation, and eastwards and westwards through its strati-graphical succession are very great.(iii) No fossils have been found anywhere in these rocks and their age is consequently not definitely known.(iv) The Foothills have obviously been the site of orogenic pressures and metamorphism, and they appear to have formed a buttress against which the Permocarboniferous rocks have been moulded by forces from east-south-east or east.(v) There is a persistent difference of 10° to 20° between the general strike of the Foothills Formation and that of the Permocarboniferous Formation along the eastern margin of the Foothills in the 35-mile tract examined by the writer. This fact cannot be accepted as proof that an angular unconformity exists because structural complexities dependent upon (iv) above can also afford a satisfactory explanation of this divergence of strike.(vi) Scrivenor has mapped the Foothills Formation as Triassic, so that its easterly dip below the Permocarboniferous must, on this hypothesis, be due to overfolding.(vii) Between the western margin of the Foothills and the Main Range granite, occur rocks, many of them strongly metamorphosed, which may originally have been calcareous shales, pyroclasts, and impure limestones, presumed, on lithological grounds, to be of Permocarboniferous age. Their alteration has been so profound that no transitional types have been discovered between thorough-going amphibole- and epidote-schists and the presumed parental calcareous sediments. Metamorphosed argillaceous and arenaceous rocks accompany them.

Description: A series of hypersthene-bearing rocks of plutonic aspect from an area east of Mount Kenya is described, with the assistance of modal analyses. A petrographic classification of such rocks, somewhat more detailed than is usually employed, is suggested, with provision for hornblende-rich types. Associated rocks are briefly described.

Description: (1) The Carbonicola fallax group of shells, which characterize the Lenisulcata Zone of the Coal Measures, is an extremely variable one comprising a wide range of forms, between which there appears to be perfect gradation.(2) The hinge of the group is also a highly variable feature, bearing little relation to the outline of the shells. Its variation, however, is more fully known in small forms than in large ones.(3) Evidence submitted in the present paper indicates that, although the hinge pattern of the C. aquilina group may not be as constant a feature as has hitherto been supposed, the group is distinct from that of C. fallax. There is no evidence suggesting genetic relationship. A basis for the distinction between internal moulds of C. aquilina and C. fallax is fully described.(4) The basic features of the hinge of the C. fallax group are essentially those which characterize the Carbonicola pseudorobusta–C. communis group of the Ovalis Zone. While certain of the hinges of the larger shells appear typical of the latter group there are a number of other patterns which have not previously been described in the Carbonicolidae.(5) The hinge features of the C. fallax group appear less specialized than those of shells from the Ovalis Zone, especially Carbonicola pseudorobusta Trueman (MacLennan, 1944).(a) Large strong teeth have not been seen. Definite small teeth are not commonly developed. It is usual to find gentle swellings on the hinge plate corresponding to depressions in the opposing valve. Some forms are quite edentulous.(b) Only one tooth has been found in either valve, although more than one swelling or depression may be present. There is no approach to the more complicated patterns figured by MacLennan (1944).(c) In most cases engagement of the dental apparatus would only take place as the valves opened. Notches or sockets in the hinge plate are not necessarily opposed by teeth or swellings, but they would have been more or less filled as the opening continued, when the hinge plates apparently rolled against one another.(d) In a community of small shells there is evidence to suggest that in several cases the hinge margin of the left valve slightly overlapped that of the right for a short distance anterior to the umbo.(6) The range of variation of hinge characters in a community is very large. Collections from different horizons, however, may indicate individual peculiarities or tendencies in the variation. Whether these owe their origin to local conditions or evolution is not yet clear.(7) The hinge of Anthracomya from the Lenisulcata Zone is as yet little known. What evidence there is points to a hinge similar to that of small Carbonicola showing the same type of variation.

Description: In the lower parts of its course a river deposits material derived from the upper parts, this deposition being due to loss of velocity. As a deduction it seems to follow that this alluvial deposit (using the term “alluvial” in a rather wide sense) should occur as two strongly contrasted types as regards size of particles.

Description: During recent years much attention has been given to the recognition of rock-structures which have been produced by the slumping and sliding of bedded deposits on the sea-floor during or soon after their accumulation, but as it is often difficult to distinguish between structures so formed and those which are the result of tectonic movements which occurred long subsequent to the deposition and consolidation of the rocks affected, it is my purpose to record certain minor bedding-structures which clearly owe their origin to such later tectonic movements in the hope that structures of this origin may more readily be distinguished from those produced by slumping. It is true that the occurrence of movements parallel to the bedding is suspected to have been widespread, and, among others, Boswell, Cobbold, and Greenly have recorded examples from this country (1937, 1904, 1919), yet, because of the general scarcity of direct evidence whereby the magnitude and frequency of such movements can be proved, it would seem to be of importance to describe the structures when the evidence of their later origin is manifest. It is for this reason, and with a view to supplementing the very little information on this topic usually contained in works on structural geology, that it has been thought advisable to make known some of the details of the minor bedding-structures which are visible in particularly instructive outcrops in the cliffs and on the foreshore of the coast of North Cardiganshire.

Description: In his monograph published in 1898, “Description des Ammonites des Couches à Peltoceras transversarium (Oxfordien Supérieur) de Trept (Isère),” A. de Riaz figured just under 100 ammonites, in 19 folio plates, of which 15 were devoted to the genus Perisphinctes. This work made known to geologists one of the most important Upper Oxfordian ammonite localities in the world, of special interest from its position in the Rhone valley, on the borderland between the Jura and the North-West European and Tethyan provinces. But in spite of the excellence of de Riaz’s photographs, their value is much reduced by the lack, in most cases, of either ventral views or whorl-sections, and by the failure to show septal sutures. Further, many of the photographs are more or less reduced, although stated to be of the natural size. The difficulty of identifying species from de Riaz’s work, therefore, is great; especially since for identification of members of the genus Perisphinctes a series of specimens at different growth-stages is usually indispensable.

Description: X.SummaryThe Cockburn Law intrusion is a small sheeted boss of late Caledonian age, intruded into Silurian rocks of Llandovery age.The following are the chief stages in its formation:—1. The earliest igneous activity was the intrusion of basic rock, now only found as xenoliths. This intrusion was followed at some later stage by—2. The main plutonic magma which assimilated the basic rock and country rock to produce the following hybrids—(a) Hybrid hypersthene diorite, from contamination by the Silurian pelites and greywackes.(b) Hybrid diopside diorite, from contamination by the basic rock.(c) Hybrid pyroxene diorite, from contamination by material from both basic igneous and sedimentary rocks.3. After the consolidation of the marginal hybrids the main body of the magma began to solidify, but had time to differentiate in place to give a composition ranging from adamellite through granite to granophyric microgranite.4. The heat from the intrusion metamorphosed the Silurian sediments to biotite cordierite hornfels which grade insensibly into the hybrid hypersthene diorite.5. Following the consolidation of the plutonic mass there was considerable activity by vapours to form pneumatolytic products, while differentiation of the residual magma produced the aplitic, acidic, and lamprophyric dykes.The intrusion may form a cupola from a bathylith, which may possibly belong to a series of bathyliths lying in a Caledonian direction from Newry to the Firth of Forth.

Description: Growth and variation in a single species from a thin bed at one locality are examined statistically. The different dimensions are shown to be allometrically related both to each other and to the volume of the shell. It is argued that total width is the best measure of age of the individual and it is shown that at a certain width there is a break in the continuity of growth of the length and thickness.

Description: Detailed mapping of a small area has shown that the Eilde Schist undergoes marked variations of facies when traced southwards from Loch Leven. Through the appearance of interbedded quartzite the normal schist of the western outcrop passes into a banded facies, while much of the banded facies of the eastern outcrop is believed to pass into massive quartzite mapped as Elide Quartzite. This sedimentary transition, rather than tectonic causes, probably accounts for the rapid variations in thickness of the two stratigraphical units. An additional factor controlling the thickness of the Elide Schist belonging to the eastern outcrop is the existence of an erosional surface at the base of the succeeding Binnenian Quartzite. The possible significance of these factors in the geology of the country north of Loch Leven is discussed briefly with special reference to some of the minor slides.

Description: Though good examples of plunging cliffs surviving as such are now rare, this form of shoreline was probably commoner in the initial stages of the current (postglacial) cycle of marine erosion. Most cliffs now bordering the sea, whether developed from initially plunging cliffs or not, have already receded some distance from the initial shoreline.As plunging cliffs may, because of reflection of waves from them, enjoy some immunity from direct frontal attack, the headlands which they truncate may be more vulnerable to marine erosion on the flanks, where the slopes partially submerged by shift of ocean level are less steep. Flank attack may lead to resection of the headland in such a way that eventually it will again end distally in a straight line of cliff; but at an intermediate stage of this resection cycle the terminations of headlands are characteristically scalloped, while at a penultimate stage of resection the salient of submaturity may be reduced to a row of stacks, the “needles” stage

Description: Active or recently-active, large-scale quarrying operations within the Carboniferous Limestone Series of this area, and ranging in location from the near-junction areas to points about half a mile removed from the southern boundary of the main littoral Trias outcrops, have afforded excellent sections displaying remnants of a former Triassic cover. It is considered unlikely that the latter outliers, of limited dimensions, occur in areas further removed than about one-third of a mile south of the existing limits of the main Triassic outcrops.

Description: Thin bands of fibrous calcite occur in the Carboniferous reef limestones of northern England and have been regarded as bands of primary tufa within a marine limestone series. A study of these fibrous bands has been carried out and the results show conclusively that they are in fact secondary recrystallization structures.