volved in their first appearance after the genera which they might, otherwise, be supposed to connect.

The author is also of opinion, that the simultaneous occurrence of twelve primitive, cosmopolitan types at the base of the second Silurian zone (=L.S.) is absolute proof of their independent origin. It must, however, be noted that the assumed absence of all Cephalopods and Acephala in the primiordial zone rests solely on negative evidence, and testimony of that nature is subject to continual modification, of which the long controverted existence of fishes in the Upper Silurian rocks and of Mammalia in the Purbecks may serve as examples. It is probable, also, that Evolutionists will be inclined to regard the wide distribution of the so-termed primitive types as indicating their antiquity, and they will not, therefore, share M. Barrande's ideas as to the utter impossibility of the discovery of a centre of development in some of the unexplored Cambrian areas. It may be added that in the Lower Tremadoc rocks of St. Davids, in South Wales (now classed on palæontological grounds as Upper Cambrian), Mr. Henry Hicks has already recorded the presence of one species of Orthoceras and twelve of Lamellibranchiata.

In concluding his investigations M. Barrande alludes in eulogistic terms to the admirable memoir by Mr. Thomas Davidson' on "What is a Brachiopod?" He refers, likewise, to the publications of M. Grand'Eury on the Carboniferous flora of Central France, and to the views expressed by Mr. Carruthers in his address to the Geologists' Association,' as being in complete accordance with the results of his own researches, and thus considers it manifest that no support to the theory of Evolution can be derived either from the Vegetable Kingdom, or from the Brachiopoda, Crustacea, and Cephalopoda in the animal domain.

The foregoing Table (pp. 40-41), compiled from five of the author's, indicates the chief points of his classification, the geological, and geographical horizons of the primitive types, the vertical distribution of the families Nautilide, Ascoceratide, and Goniatida, and the number of species of each genus in which the embryological characters have been satisfactorily determined.3 A.C.

REPORTS AND PROCEEDINGS.

GEOLOGICAL SOCIETY OF LONDON.-I.-Nov. 21, 1877.-John Evans, Esq., F.R.S., D.C.L., Vice-President, in the Chair.-The following communications were read:

1. "On the Glacial Deposits of West Cheshire, together with Lists of the Fauna found in the Drift of Cheshire and adjoining Counties." By W. Shone, Esq., F.G.S.

The conclusions arrived at by the author in this paper were as 2 GEOL. MAG., Dec. 1876.

1 GEOL. MAG., April, May, June, 1877.

3 For a previous review of M. Barrande's labours on Cephalopoda, see GEOL. MAG. 1870, Vol. VII. p. 486.

follows:-Like Prof. Hull, he distinguished a triple division of the deposits under consideration. 1. The Lower Boulder-clay, or, as he preferred to call it, Lower Glacial Drift, resting immediately upon the eroded surface of the Keuper, consists for the most part of compact clay, containing numerous and large striated erratics, together with a fauna of Scandinavian type, the Gasteropoda being generally filled with fine silt containing Microzoa. The author believed that the shells found in this deposit were principally distributed by ground-ice, which took them up and floated them off the shore. 2. The Middle Sands and Gravels, or Interglacial Drift of the author, consist chiefly of sands and gravels containing few (if any) glaciated stones. The fauna of this division is Celtic, with a few Scandinavian species derived from the Lower Boulder-clay; the shells were distributed principally by currents; and the Gasteropoda seldom, if ever, filled with sand containing Microzoa. 3. The Upper Boulderclay or Upper Glacial Drift, is composed for the most part of clay not so compact as the Lower Boulder-clay, and containing fewer and smaller glaciated stones, which are more abundant near the base. The fauna is Scandinavian at the base of the beds. The shells were distributed principally by ground-ice, and those of southern type derived from the Middle Sands and Gravels. The Gasteropoda are chiefly filled with silt containing Microzoa. The paper was accompanied by lists and tables of fossils, a large collection of which was exhibited in illustration of the paper.

2. "The Moffat Series." By C. Lapworth, Esq., F.G.S.

The fossils found in the highly convoluted Lower Silurian rocks of the southern uplands of Scotland are usually restricted to certain narrow bands of black carbonaceous and Graptolitic shales, which, from their especial abundance in the neighbourhood of the town of Moffat, Dumfriesshire, are known to geologists as the Moffat Shales or Moffat Series.

The most perfect section of the black shales visible within the Moffat area is exhibited in the cliffs of the gorge of Dobb's Linn, at the head of Moffatdale. It was shown by the author that they are here disposed in a broken and partially inverted anticlinal, which throws off on both sides the basal beds of the surrounding nonfossiliferous grey wackes. They are distinctly arranged in three successive groups or divisions. Each of these divisions is distinguished by special lithological characteristics, and possesses a distinct fauna. To the lower and middle divisions a few fossils are common, but between the middle and upper divisions the palæontological break is complete. These divisions, again, are naturally subdivided into several zones, each characterized by special species, or groups of species.

A larger exposure of the same deposits occurs at Craigmichan, a few miles to the south-west, where the beds of the lower division are shown to a much greater depth than at Dobb's Linn. In these two localities the general succession of the Graptolitic shales is as follows:

With the aid afforded by these sections, the thorough investigation of the ten subparallel black shale-bands of the Moffat area is rendered a matter of ease and certainty. Of these, the four bands lying to the south-west of Saint Mary's Loch are the most continuous. They were described in detail by the author, and it was shown that in each the only strata apparent are indisputably those of the typesections of Dobb's Linn and Craigmichan, with which they agree zone for zone in sequence and in all their characters, mineralogical and zoological. Here, also, the beds are arranged in greatly elongated anticlinal forms, the axes of which are, as a rule, inverted. In any single transverse section, the succession of the beds on the opposite sides of the median line of the band is identical, and the highest zone of the black shales everywhere passes up conformably into the basal bed of the surrounding greywackes. The varying width of the band is dependent simply upon the varying elevation of the crown of the anticlinal. Where the band is of least diameter, only the highest beds of the Birkhill shales rise from below the greywackes. As the band expands, the underlying zones emerge one by one in its centre, till finally, in the widest exposures, we recognize the deepest strata of the Glenkiln shales.

It was shown by plans, sections, and descriptions of every exposure of consequence within the Moffat district that precisely similar results are arrived at with respect to the remaining black shalebands. To the south of Moffatdale, the Moffat beds agree essentially with those of Dobb's Linn; but to the north the whole formation diminishes in collective thickness, and the highest division gradually loses its fossiliferous black shales.

These facts place it beyond question that all the carbonaceous and Graptolitiferous shales of the Moffat area are portions of one and the same originally continuous deposit-the Moffat Series, which is now the oldest visible rock-group in the district, being everywhere inferior to the prevailing greywackes, through which it invariably rises from below in greatly elongated anticlinal forms.

In the rigid restriction of distinct groups of fossils to a few feet of the succession, the rocks of the Moffat series resemble the thinbedded Silurians of Scandinavia and North-eastern America. From analogy it may be suspected that they similarly represent an enormous period of time. The correctness of this inference is demonstrated by the evidence afforded by the known geological range of

their organic remains. The Graptolithina of the Lower or Glenkin division are those of the highest Llandeilo Flags of Wales, the corresponding Middle Dicranograptus-schists of Sweden, and the Norman's Kiln shales that underlie the Trenton (Bala) Limestone of New York. The Hartfell species occur in the Bala beds of Conway, etc., the higher Dicranograptus-schists of Sweden, and the Utica and Lorraine shales that overlie the Trenton Limestone. Those of the Birkhill shales agree almost species for species with the fossils of the Coniston Mudstone of Cumberland, the Kiesel Schiefer of Thuringia, and the Lobiferous beds of Sweden, which lie at the summit of the Lower Silurians of their respective countries. Hence

it may be considered certain that the Glenkiln shales are of highest Llandeilo age, that the Hartfell shales stand in the place of the Bala or Caradoc of Siluria, and that the Birkhill shales correspond to the Lower Llandovery.

The insignificant thickness of these three formations in the Moffat district is in strict agreement with the well-known north-westerly attenuation of the Lower Silurian rocks in Wales, England, and in Western Europe generally.

It was pointed out that these results, when carried to their legitimate conclusion, harmonize all the apparently conflicting facts hitherto collected among the Lower Silurians of the south of Scotland. We have a complete explanation of such difficulties as the remarkable lithological uniformity of the predominating strata, the absence of associated igneous rocks, the peculiar localization of the fossils, their identity along certain lines, and their rapid and peculiar impoverishment along others. We reduce, at a single stroke, the apparently gigantic thickness of the South Scottish Silurians to reasonable limits, and at the same time bring them into perfect harmony with those of Western Europe and America.

II. December 5, 1877.-Prof. P. Martin Duncan, M.B., F.R.S., President, in the Chair. The following communications were

read:

1. "On the Building-up of the White Sinter Terraces of RotoMàhànà, New Zealand." By the Rev. Richard Abbay, M.A., F.G.S. The author described the structure and mode of formation of the so-called “White Terrace" of the Roto-Màhànà, which is produced by a deposit of silica from the water of a geyser situated on the side of a small hill of rotten rhyolitic rock, about 100 feet above the surface of the warm lake (Roto-Màhànà), into which the water from the geyser finally flows, and the foot of the siliceous terrace projects. The geyser basin, which is between 300 and 400 feet in circumference, has steep walls broken through only on the side towards the lake, where the water flows down to form a succession of terraces, which are really shallow basins, over the outwardly inclined edges of which the water flows, depositing the dissolved silica in a white subflocculent form on the edges and bottoms of the basins in proportion as the water cools. The author showed how this arrangement produced the peculiarly formed siliceous deposit of the terraces, and that as the growth of the latter is evidently up

wards as well as outwards, it seems probable that the geyser pipe has slowly worked its way up the hill by the solvent action of the heated water from the level of the lake to its present elevation.

2. "Additional Notes on the Dimetian and Pebidian Rocks of Pembrokeshire." By Henry Hicks, Esq., F.G.S.

The additional facts communicated by the author show that at a distance of about 10 miles to the east of the Dimetian axis of St. David's there is another ridge of these rocks, which also runs nearly parallel with it. This is also flanked by Pebidian and Cambrian rocks, and made up of rocks like those in the St. David's axis.

The Dimetian formation, so far as it is at present known, consists chiefly of the following rocks:

1. Quartz porphyries, containing frequently perfect quartz crystals (double pyramids), subangular masses of quartz, and crystals of felspar in a felspathic matrix.

2. Fine-grained greyish quartz-rocks, very compact, and interstratified with the above.

3. Ashy-looking shales of a dull green colour, sometimes highly indurated, but usually showing lines of lamination. Microscopically these show basaltic characters, and are probably greatly altered interbedded basaltic lavas.

4. Compact granitic-looking rocks.

5. Quartziferous breccias.

6. A series of compact quartzites and crystalline schists, interstratified by green and purple altered basaltic lavas, with a slaty and schistose foliation, and by some dolomitic bands.

Of the Pebidian formation new areas were added, and the portions described in the author's previous paper were further extended, and details as to the chief mineralogical characters added. At the base of the series resting unconformably on the Dimetian is seen an agglomerate composed of large angular masses of a spherulitic felstone, pieces of quartz and quartzites, indurated shales, crystalline schists, etc., cemented together by a sea-green matrix of felstone. These are followed by conglomerates of the same materials, which are again succeeded by indurated shales, often highly porcellanitic in character, with a conchoidal fracture.

These are followed by a thick series of silvery white and purplish shales and green slates, alternating with fine and rough ashes, often conglomeratic, hornstone breccias, felstone lavas, etc.

The series, as exhibited at St. David's, has a thickness of over 8000 feet; and as it is everywhere, so far as yet seen, overlapped unconformably by the Cambrians, it may probably be of much greater thickness. It evidently consists very largely of volcanic materials, at first derived from subaerial, but afterwards from submarine volcanos. These materials, however, were also undoubtedly considerably aided by sediments of a detrital origin.

The whole series shows that the sediments have undergone considerable changes, but yet not sufficient to obliterate the original characters, and the lines of lamination and bedding are usually very distinct. That they were altered nearly into their present state