scales may be mistaken for petals, and the fractured axis for the stamen and pistillum.

The seeds are concealed by the leaflets.

(Zamites lanceolatus.)

22. COLLYWESTON TILESTONES.-Near Stamford, in Lincolnshire, the lowermost visible strata are Lias-clays, upon which are spread the ferruginous beds of the Inferior Oolite; and above are beds of laminated calcareous stone, locally termed the "Collyweston slates," from being quarried in that neighbourhood.* These deposits, therefore, appear to

*See Quart. Journ, Geol. Soc. vol. ix. p. 335.

occupy the same geological position as the Stonesfield tilestone of Oxfordshire and of the Cotteswold hills, and contain similar marine shells. They are associated with marly limestone. The fossils are shells of the genera Pteroceras, Nerinæa, Lucina, Modiola, Trigonia, &c., with numerous fragments of the leaves of ferns (especially of Pecopteris polypodioides), and of cycadaceous plants. These beds have been regarded by Captain Ibbetson and Mr. Morris as the equivalents of the carbonaceous shales of Scarborough and Gristhorp Bay; in fact, as the seaward extension of those fluviomarine strata. Those of Stonesfield appear to have been synchronous, but deposited still farther from land.

23. COAL-BEARING OOLITE OF BRORA.-Carbonaceous fluvio-marine deposits of a similar character to, and of the same Lower Oolite age as, those above described occur in the north of Scotland.* At Brora, on the south-east coast of Sutherlandshire, intercalated between the Middle or Oxfordian Oolites and the Lias, there is a series of deposits consisting of, 1st, shelly limestones, representing the Cornbrash and Forest-marble; 2. sandstones, shale, and ironstone, with remains of land-plants; 3. shelly limestone with fossil wood; 4. sandstone and shale with plant-remains, and containing towards the top two beds of coal. In the neighbourhood of Elgin also, and on the north-east coast of the Isle of Skye, shales and sandstones with impressions and remains of similar plants are met with, superimposed on the Lias.t

The fossil plants are for the most part of the same type as those of Yorkshire, and are associated with fresh-water or brackish water shells of the genera Cyclas or Cyrena, Unio, and Paludina. Tellina and Perna have also been found; and

* For a general view of the geological phenomena of Scotland, the reader is referred to the instructive little volume by Prof. James Nicol, entitled, A Guide to the Geology of Scotland, 1844.

+ Sir R. Murchison, Geol. Trans. 2 ser. vol. ii. p. 293; Mr. Robertson, Geol. Proceed. vol. iv. p. 173, and Geol. Journ. vol. iii. p. 113; and Prof. E. Forbes, Geol. Journ. vii. p. 107.

Cyprida (p. 419) occur in profusion. Scales and teeth of numerous small ganoid fishes, of genera common in the Oolite (Hybodus, Lepidotus, and Acrodus), abound in some of the layers of clay fragments of plates and bones of Chelonians are among the few reptilian relics hitherto observed.

These coal-bearing deposits have evidently had the same origin as those of north-eastern Yorkshire, where Uniones and Cypridæ are associated with Ferns, Zamiæ, Thuyites, and other terrestrial plants. Taken as a whole, the fluviomarine intercalations of the Oolite must be regarded as local accumulations of the spoils of the land, transported into the sea by the agency of rivers; the presence of coal depending on the streams being largely charged with vegetable remains; or perhaps, in some cases, to the subsidence and covering up of swamps and lagoons rich with vegetable growths. They belong to a period long antecedent to the deposition of the Wealden, which was subsequent to the formation of the upper Oolites.

24. JURASSIC COAL-FIELD OF EASTERN VIRGINIA.-One of the most remarkable features in the geology of the United States of North America, as contrasted with that of Europe, consists in the absence of deposits yielding jurassic fossils such as, throughout large tracts in England and Europe, represent the vast interval of time that must have elapsed between the close of the Triassic and the commencement of the Cretaceous epoch. Some time since, it was suggested by Professor W. B. Rogers, that an extensive coal-field in * Eastern Virginia* belonged to the Jurassic period; and Sir C. Lyell coincides in this opinion. This coal-field is about twenty miles from north to south, and from four to twelve miles in breadth from east to west. It is situated in a

There are two coal-fields in the State of Virginia: the remarks in the text exclusively refer to the Eastern coal-field,—that near Richmond; the coal-measures in Western Virginia belong to the ancient Carbonifer. ous system.

granitic region, and the lowermost bed of coal rests upon granite. Quartzose grits, sandstones, and shales are intercalated with the coal, as in the carboniferous system of Europe. Beds of rich bituminous coal, one being in some places from thirty to forty feet thick, occur in the lower division.*

The fossil plants resemble those of the Oolite of Yorkshire (Pecopteris Whitbiensis, Equisetum columnare, some species of Zamites, Taniopteris, Neuropteris, &c.), differing specifically, and most of them generically, from those of the older coal-formations. From the upright position of many of the Equiseta, Sir C. Lyell infers that the vegetables which produced the coal grew on the spot where they are now found, and that the strata were formed during alternate subsidences and elevations of this part of Virginia. They contain fossil fishes (Tetragonolepis and Catopterus†) related to European Liassic species; and numerous Cypride and Estheria, the latter of which, under the name of Posidonomy, are characteristic of some strata of the European Trias. Prof. Rogers finds reasons to regard this coal-field of Eastern Virginia as belonging to the same series of deposits as the red sandstones and coaly shales of Carolina to the South, and of Maryland, New Jersey, and Connecticut, to the North. These beds are characterized by the local occurrence of Estheria and Cypride, reptilian bones, and plant-remains; and in Connecticut, by numerous impressions of supposed birds' tracks. They have been variously referred to the Trias and the Permian series; but probably more or less fully represent in time, as extensive land and

* Plant-beds and coal of similar characters as the above have been found near the Rocky Mountains, at Raton Mountain and Muddy River.

+ Sir P. Egerton's genus Dictyopyge consists of some of Mr. W. C. Redfield's Catopteri. See Silliman's Journal, 1856, vol. xxii. p. 357, and Geol. Soc, Journal, vol. iii, p. 275.

fresh-water formations, the Upper Trias and Lower Jurassic periods.*

In India and South Africa, and probably in Australia, similarly characterized deposits, possessing both Triassic and Jurassic elements, are recognized.†

In the Chatham coal-field (North Carolina), of this age, Dr. Emmons has discovered some lower jaws of a small species of mammal, which he has named Dromatherium sylvestre. They much resemble some of the little marsupial jaws from Stonesfield and Purbeck. Dr. Emmons has also figured and described § a fossil sacrum of a bird from the same series of deposits,-referred by him to the Permian age.

25. THE LIAS.—The lowermost group of the Oolitic or Jurassic system, termed the LIAS, consists of stratified blue and grey marls, clays, and limestones, amounting in total thickness to from five hundred to one thousand feet, and abounding in many peculiar fossils. The principal lithological features are the uniform aspect and distinctly stratified character of the limestones and intervening argillaceous layers; the most constant subdivisions are those mentioned in the table, || p. 490.

* The Wealden may in like manner be said to be tu equivalent of the Upper Jurassic and Lower Cretaceous cres.

See Mr. T. R. Joues's remarks on this subject in the Geol. Soc. Journ., vol. xii. p. 376.

American Geology, part vi 35, 1857.

Ibid. p. 148.

|| In 1856 Dr. T. Wright, of Cheltenham, published in the Quarterly Journal of the Geological Society a paper, to show that the sands usually referred to the Inferior Oolite in the West of England contain fossils of the Liassic type, and should be classified as with Lias, and not with the Lower Oolite. Although Mr. Hull, of the Geological Survey, has accepted Dr. Wright's views, and carried them out in his description of the geology of the country around Cheltenham (Memoirs Geol. Survey, 1856), yet there are too many dissentients to these views amongst experienced geologists, and too many openings for criticism in