The sudden disappearance of groups of animals, which have existed through long periods of time and have attained a high degree of specialization, is a phenomenon of which many instances will occur to every student of Palæozoology. For instance, to mention only two cases in illustration, we may refer to the disappearance of the Dinosaurs at the end of the Secondary period, and that of the North American Titanotheres in the Miocene. Of the proximate causes of this extinction little is known: they must have been either inherent in the organisms themselves, or have been connected with the relations of the organisms with their environment; probably in every case several factors co-operated to bring about the observed result. In a recent paper by Mr. C. B. Crampton (Proc. Roy. Phys. Soc. Edinburgh, vol. xiv, p. 461) a possible inherent cause of extinction is suggested. It is impossible to do justice to this interesting paper in a short note, but the gist of the argument seems to be as follows:—In the original unicellular organism the possibilities of variation are almost infinite, but as soon as evolution along any line begins, these possibilities are restricted, and become more and more so the more highly specialized the animal is; in short, the potential variation of an organism becomes less and less as specialization advances. Furthermore, under the influence of natural selection, in each generation the individuals which tend to vary in the same direction will survive, while at the same time, as already pointed out, their capacity for variation becomes more and more restricted.

The entire collection of Wenlock fossils made by T. W. Fletcher, Esq., which is now in the Woodwardian Museum, affords unsurpassed facilities for studying the material on which a large number of species of trilobites were founded. Particularly is this the case with those of the genus Lichas, and a recent examination of the types and other specimens which Fletcher used in writing his paper “Observations on Dudley Trilobites” (Q.J.G.S., 1850, vol. vi, pp. 235–239, pls. xxvii and xxvii bis) has led me to make the following notes upon them. I have also had the privilege, through the kindness of Dr. Arthur Smith Woodward, F.R.S., of examining the specimens in the British Museum (Nat. Hist.), Cromwell Road.

The form of the deposits that are taking place on the sea-bottom at the present day is one of the essential elements required to be known when we wish to interpret the submarine contours, as throwing light on the submergence or elevation of the land in late geological times, or when we propose to use the variation of thickness of the strata deposited during any epoch as an indication of the position of the shore-lines at that time.

In the case of deposits in small or temporary masses of water, their form and arrangement may sometimes be observed directly; but in the case of the deposits in the sea, where we can neither remove the water nor make borings beneath it, we can only avail ourselves of theoretical considerations.

It might have been expected that the original form of various sedimentary deposits would have been considered in detail long ago, but as a matter of fact the few writers who have touched upon the question have mostly been content with the assumption that deposits taken as a whole are thickest near the source of supply, and the figures given in illustration of the arrangement of various kinds, and thereby the shape of each, are remarkable for their variety.

As the theoretical results at which I have arrived differ fundamentally from the ordinary assumptions, it is to be hoped that some one will be able to point out the fallacy, if any, which has led me astray, and to explain more satisfactorily the observed features which appear to confirm the theory.

At Towan Head and in the cliffs of Fistral Bay, near Newquay, there is seen, at a few feet above high-water mark, the remains of the Pleistocene Raised Beach. This consists of pebbly beds associated with ancient blown sands, sometimes of considerable thickness. Above this series of deposits comes the Head or Rubble Drift, formed during a greater elevation of the land. These beds have been fully described by many authors—De la Beche, W. A. E. Ussher, Sir Joseph Prestwich, and others. While capping the Head and Raised Beach, and on the top of the cliff, there is a series of more recent Æolian sandy beds.

The following notes were made during the little time I was able to devote to leisure while staying at Camborne in order to study the methods there employed of mining and dressing the tin-bearing rock. They therefore deal only with places within easy reach of that town.

Having been favoured by Mr. Walter Barratt, of Sunnybank, Newquay, Cornwall, with the opportunity of examining two Trilobites from the Devonian slate-rock—(1) from a cove near Trevose Head, (2) from the shore of the mainland opposite Trescore Island, Porthcothan, Cornwall,—I gladly avail myself of his permission to publish a note thereon.

During a preliminary traverse of the Lower Cretaceous outcrop in the Midlands last June, I visited Faringdon for the first time, and examined the famous sections in the ‘Sponge-gravels.’ My chief aim was to obtain some evidence by which the relative position of these beds in the Lower Cretaceous series might be determined. The greater part of the fauna was so anomalous and peculiar that it afforded little or no assistance towards this purpose, and the only common fossil which gave definite promise of service was the fragmentary Belemnites, which I found in unexpected abundance. It is true that I had previously noticed a few specimens among the Faringdon fossils in the Natural History Museum (from the Caleb Evans’ Collection) and in other public collections, and had seen references to Belemnites in descriptions of the ‘Spongegravels’; but I went with the impression that its occurrence was rare and exceptional, whereas I found that it could be collected plentifully from every pit, though always in a more or less worn and fragmentary condition, and generally encrusted with small oysters, serpulæ and polyzoa, and perforated by marine borers. The scant attention which the fossil has hitherto received is probably due to the prevalent opinion that it is derivative from the Jurassics, but this opinion is almost certainly erroneous, as I shall now try to show.

In the large number of specimens which I obtained only one species appears to be represented, and this species cannot, I think, be matched among Jurassic Belemnites.

In the neighbourhood of Foxdale, Isle of Man, and especially on Granite Mountain, the ground is strewn with numerous blocks of quartz. Many of them are of large size, 10 feet or more in diameter.

On the slopes of South Barrule similar blocks are found in great profusion, and they can be traced across the hills to the west coast. North of Foxdale other bands are found, some of which are inserted in the geological map. They lie principally in the altered slates of the Barrule Series, and have a general trend corresponding with the main axis of the island, from north-east to south-west. In places they are seen to be in sitû, and where the granite mass of Foxdale intervenes the general direction changes, and is principally tangential to the intrusion.

Numerous micro-granite dykes extend along the axis of the island in the same direction.

In an old quarry at Renshent on the north margin of the granite several quartz veins are seen to traverse the granite itself. They can be traced along the floor of the quarry and up the vertical face about 30 feet high.

One of these, about 3 feet in width, shows perfectly sharp margins when cutting through the granite, dips at 65° W., and strikes 10° E. of S. It consists mainly of quartz, some clear and some white and opaque, but on entering the granite it changes locally to a pegmatite. The pegmatite contains, in addition to the quartz, large felspars, some over 3 inches long, perfectly formed, and showing crystal faces, and mica in crystals over an inch in diameter.

In the December number of this Magazine Mr. Buckman complains that the use of his term hemera has been widely misunderstood. He says that it was never intended to be used for a subdivision of a zone, but solely as a chronological term to indicate the time during which the beds composing a zone were deposited, just as the term age is now generally accepted in a technical sense to mean the time during which a stage was deposited.