On studying a topographical map of Lake Geneva, two characteristic features strike one at once. There is, first of all, the division of the basin into two parts of different orientation—the “Grand Lac” set almost E.W., and the “Petit Lac” deviated by about 60° towards the S.S.W. The inhabitants of the region have always distinguished between the “Grand Lac”, also called “Haut Lac”, and the “Petit Lac”. The former has a depth of 300 metres and consists of a single basin, the floor of which is remarkably flat whilst the second, separated from the other by a submerged ridge 66·3 metres below the surface, begins by a first fosse76·2 metres deep, followed by three others 70·1, 70·4, and 50·1 metres deep respectively. IfLake Geneva is considered as having a single origin, and if the theory of glacial overdeepening is adopted, it is very difficult to explain the ridge separating the two basins. On the other hand, the “Haut Lac”, taken alone, presents nothing abnormal, compared with other basins in whose formation glaciers have taken a large part.

Four species of Monograptus are described and the age of the strata shown to be that of the zone of M. nilssoni of the Lower Ludlow of Great Britain.

In 1844 M'Coy subdivided the genus Spirifer Sowerby into five groups, two of which, Brachythyris and Martinia, were characterized by “the presence of a hinge-line shorter than the width of the shell”. Brachythyris included forms “in which … the longitudinally-ribbed surface of Spirifera is united with the short hinge line of Martinia”. The latter included “the smooth spirifers”. M'Coy's subdivisions, however, have not been much used. More recently Mr. S. S. Buckman2 has shown that the smooth forms grouped by M'Coy and others in Martinia are the catagenetic members of several spiriferid stocks. Buckman considered that Martinia and Brachythyris were distinct from the other spirifers in their shape and in their lack of dental plates.

The internal structures and development of the genus Holocystis Ed. and Haime, of which only one species, the type, has been recorded, have not previously been described. It is the purpose of this paper to repair the omission. This Aporose genus is interesting in that it exhibits certain characters normally well developed amongst Rugosa and in possessing four principal septa arranged in a cruciform manner within the calice, instead of having its septa merely arranged on the hexameral plan characteristic of normal Aporosa. I am greatly indebted to Dr. Stanley Smith for the loan of certain specimens, and for much helpful criticism and advice, and to Professor S. H. Reynolds for access to, and use of, material in the geological collections of the University of Bristol.

The pebble about to be described was found in the Middle Louth Seam at Swannington Colliery, near Ashby-de-la-Zouche, in Leicestershire, and was presented to the writer in the year 1899 by the late Mr. Henry Copson Peake, who at that time was manager of the Swannington Colliery and also general manager of the Walsall Wood Collieries, near Walsall.

In 1915 I published a short paper in which it was shown that the Coal Measures of the Clapton area on the northern side of the Clifton-Clevedon ridge, Somerset, rested with strong unconformity upon the Carboniferous Limestone and all older rocks. Subsequently Professor S. H. Reynolds, having observed the relations at Court Hill, Clevedon, where the Carboniferous Limestone is clearly thrust over the Coal Measures, saw no reason to differ from the earlier observers, Buckland and Conybeare, the officers of the Geological Survey, and Lloyd Morgan, all of whom regarded the Main Limestone-Coal Measures junction south of Clapton as a faulted one; accordingly, on the map accompanying his paper, Professor Reynolds showed the boundary as a fault as far as the eastern limit of the Coal Measures, even where they transgress from the Main Limestone across the Lower Limestone Shales. At a later date Dr. E. Greenly, in a description of the sections at East Clevedon Gap, about three miles west of Clapton, referred to the unconformity as follows: “Whether, as believed by A. Vaughan and F. Dixey, there be unconformity, the whole of the Visean, with apparently the Lower Coal Measures as well, having been locally removed by inter-Carboniferous erosion, is a question that will not be discussed in this paper. But, independently of that question, there is reason to suspect that the base is cut out, for the lowest visible sandstones on the wooded bluffs are buckling over, as if driven forward on a thrust-plane. Should serious unconformity be eventually proved, this thrust need not be of much tectonic importance. In any case, the plane, whatever its nature, is over-stepped by the Bella-Vista Thrust-plane…”

The origin of coal is a difficult problem which is very far from being solved. The Coal Measure flora has long been extinct, and the modern representatives are feeble folk, almost crowded out of existence by plants of very different appearance and internal structure. The modern marsh flora is not primitive but secondary, and consists almost entirely of land plants which have taken to the water habitat again, just as the whale, porpoise, and seal are land animals which have gone back to rejoin their remote ancestral relatives in the sea. Homologous comparisons between past and present are therefore practically impossible, but some common pool developments of to-day may provide useful analogies if nothing more.