The 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.

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.

The invaluable Presidential Addresses by Professor H. H. Read, entitled “Meditations on Granite”, Parts I and II, read to the Geologists’ Association in 1943 and 1944, seem to have aroused a great deal of interest in petrological quarters, more especially as these “meditations” are painted against the lively background of the historical development of ideas embracing a whole century and a half. Professor Read’s “meditations” are the more remarkable since they lead him to conclusions almost diametrically opposed to those propounded by Professor P. Niggli in an address delivered to the Zürich Geological Society at the February meeting of 1942, although both reviewers rely on about the same scope of historical “evidence”.

(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.

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.

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).

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.

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.

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).

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.

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.

The River Amber on its way from the Erewash Valley Coalfield to its junction with the Derwent near Ambergate crosses the upturned edges of the Millstone Grit Series. Near the point where the river enters the grit belt at Bullbridge a boring for water was put down in the grounds of the Amber Dye Works during the latter half of the year 1936. My thanks are due to the directors of Stevensons (Dyers), Limited, for giving me every facility for examining the core, and to Mr. S. G. Clift for assisting me in the examination and in collecting. My thanks are also due to Dr. C. J. Stubblefield for valuable criticisms and suggestions during the writing up of this note.

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.

Judd was one of the early workers to recognize that changes in the mineral constitution of an intrusive igneous rock, changes affecting the earlier minerals, may take place prior to the completion of crystallization. He points out that minerals, since their first crystallization, may have undergone several series of changes, totally dissimilar in kind, and resulting from causes altogether different, and that the dissolved material may be carried away from a crystal and deposited within the cavities of neighbouring crystals of different species. This process must result in the blending together in the most inextricable manner of material derived from different crystallized minerals, and the whole characters of the rock may be completely altered.

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.

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).

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.

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.