Since the publication of an earlier paper by Mr. Charles Elton and myself (1931), further Quaternary fossils from Spitsbergen have been identified by me, including a lamellibranch (Macoma) which, I believe, has not been recorded previously from Spitsbergen, but which is similar to a form described by Brøgger from the Yoldia Clay of the Oslo district.

It is proposed in the present paper to discuss certain micrometric methods applicable to the minerals of sedimentary rocks and to suggest how their graphical study may be used for the elucidation of certain problems in sedimentary petrology. The examples used are taken chiefly from the Triassic and Jurassic rocks of Yorkshire as described in Part I.1

In the type area the Ludlow Rocks generally have been divided into Lower Ludlow Shales, Aymestry Limestone, Dayia Shales and Whitcliffe Flags in upward sequence. The Dayia Shales are characterized by the presence of enormous numbers of Dayia navicula (J. de C. Sowerby). This preponderance of D. navicula in the shales immediately above the Aymestry Limestone has caused a tendency to regard beds in other localities containing this fossil as being on the same stratigraphical horizon in spite of the character of the accompanying fauna. In two recent papers on the Ludlow Rocks of the Welsh Borderland (Straw, 1937, and Earp, 1938) it has been shown that D. navicula ranges through at least 3,000 feet of strata, occurring commonly throughout this great thickness and outlasting more than one change of fauna. Although, in this area, the brachiopod ranges from the zone of Monograptus nilssoni into the Upper Ludlow it has not hitherto been recorded below the Aymestry Limestone in Shropshire. This gap in our knowledge is now filled by the discovery of specimens in Lower Ludlow Shales exposed in a small quarry 40 yards north-east of Stokewood Cottage, which is on the west side of the railway line a little over a mile south of Craven Arms. The quarry shows about 15 feet of nodular shales with thin limestone seams. The commonest fossils are Chonetes laevigata (J. de C. Sowerby), C. minima (J. de C. Sowerby), and Stropheodonta filosa (J. de C. Sowerby) which occur in large numbers on some of the bedding surfaces. Other fossils are Stropheodonta euglypha (Dalman), Delthyris sp., Orthoceras sp., Dalmanites sp., and a plectambonitid. Dayia navicula seems to be confined to a thin layer on the north side of the quarry. Graptolites referable to Monograptus cf. chimaera occur fairly commonly. About 400 yards in a south-easterly direction another small quarry exposes Conchidium Limestone which is about 170 feet stratigraphically above the beds in the first quarry.

In our earlier paper on the Petrography of the Blea Wyke Series (1) we stated our intention of describing the Blea Wyke Beds as developed alongside the Peak Fault, or as near to it as possible. This section has never been described, while the brief references to it in the Geological Survey Memoirs (2, 3) are not altogether correct. Here it is stated that “all the beds become thinner in the steep cliffs to the northwards of Blea Wyke, so that below Peak Hall, where they are again accessible, there are not more than 15 feet of the ‘Grey Beds’ and 20 feet of the ‘Yellow Beds’”.

The genus Proetus is present at three horizons in the Girvan district. The first appearance is at Balclatchie in the highest beds of the Barr Series of Lapworth (Bala); next it occurs in the Drummuck Trinucleus Shales (Ashgillian), now usually referred to as the Drummuck Group; and its final occurrence is at Newlands in the Saughhill Group (Mid-Valentian).