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It may be stated in general terms, that the Lias of England extends along the western escarpment of the Oolite, from Yorkshire to the Dorsetshire coast, forming a district which presents an exceedingly variable surface, occasioned by the disruption and subsequent denudations which the strata have undergone.

The Lias,* from its northernmost limits on the Yorkshire coast, where it underlies the strata of the Eastern Moorlands,† passes to the south of Whitby and to the east of York, and crosses the Humber near the junction of the Trent and Ouse; stretching onward beneath the low Oolitic range of Lincolnshire, it extends to the Wold hills, on the borders of Nottingham and Lincoln, to Barrow-upon-Soar; whence it continues, accompanying the escarpment of the Inferior and Great Oolite, through Nottingham, Warwick, and Gloucester. Its whole course, to within a few miles south of Gloucester, is remarkably regular, presenting an average breadth of about six miles, bounded on the southwest by the Oolite, and on the north-west by the Red Marl, which will hereafter be described. Beyond Gloucester, its range becomes intricate; its eastern limit accompanies the Oolite through Somersetshire to Lyme Regis; but the western is very irregular, feathering in and out among the coal-fields which occur towards the estuary of the Severn and the upper part of the Bristol Channel, Gloucestershire, Somersetshire, Monmouthshire, and Glamorganshire, and attended with numerous outlying or detached masses. render the course and position of the Lias in this part of England intelligible, it is necessary to state, that this disDr. Wright's arguments, to allow of our altering the present classification of these beds, which, though possibly passage-beds, and partaking of the characters of the two series, have too much in common with the Oolite to be separated from it.

* Outlines of the Geology of England and Wales, p. 261.

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+ In the Lias of the Eske Valley there are two great beds of ironstone, which are extensively worked.

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trict is occupied by three great basins of the coal-formation, encircled by the underlying Mountain-limestone and De

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LIGN. 124-SECTION FROM SOUTH OF MALMESBURY THROUGH THE MENDIP HILLS. 1. Mountain-limestone, overlying Devonian rocks. 2. Millstone-grit, underlying the coal-beds. 3. Triassic and Permian strata. 4. Lias. 5. Inferior Oolite. 6. Great Oolite. 7. Oxford clay.

(From the Geology of England and Wales.)*

vonian sandstones; one of these basins is shown in the annexed section.

The edges of these basins consist of strata thrown up at a high angle, and often nearly vertical, forming bold and precipitous ranges of hills; in the valleys, horizontal layers of Lias, with subjacent beds of red-marl (Lign. 124), are seen lying unconformably upon the highly inclined coalmeasures. I shall recur to this subject hereafter, and now only observe, that the Lias appears beneath the Oolite through the south-east of Somersetshire, and passes into Dorsetshire, where the overlying Greensand conceals it beneath the high range of the Black Down Hills.

At Lyme Regis it forms a range of cliffs, about four miles in length, and may be traced until it gradually sinks beneath the Inferior Oolite of Bridport. The skeletons of large marine reptiles (Ichthyosauri and Plesiosauri), for which the Lias is celebrated, have principally been found in the cliffs at Lyme, Watchett, Westbury, and Whitby, where the natural sections, formed by the action of the waves, well

* The inclination of the strata is very much exaggerated in this diagram, in consequence of the difference in the horizontal and vertical scales, necessarily adopted to comprise the section in a small space.

display the characters of the strata, and afford abundance of fossil remains. The Lias appears in the Western Isles of Scotland, and on the north-east coast of Ireland. The Upper Lias comprises a thin band of limestone, rich with remains of insects and fish, which has been traced from Somersetshire and Gloucestershire into Northamptonshire

and Lincolnshire.*

In the north and south-east of France, and over a large area in Germany, the Lias, with its peculiar fossils, accompanies the Oolite. One species of Gryphite (Gryphæa incurva, Lign. 117, fig. 6), which is so abundant in the Liassic strata of England, on the Continent forms a limestone (Calcaire à gryphites), which, like the Sussex-marble and many other such rocks, is composed of shells cemented together by a calcareous paste. In Wirtemberg the Lias presents the usual characters of that of England, and contains remains of Ichthyosaurs and other reptiles.†

In the valley of the Arve, in Switzerland, the Lias-clays are of great thickness, and, owing to the ancient effects of igneous or metamorphic agency everywhere apparent in the Alps, have a schistose character, strongly assimilating them to the primary slates.

In Russia oolitic deposits cover detached districts, from the Icy Sea to the Caucasus in the south; and in Russia Proper there are shales and sands referable to the Middle or Oxford Oolite; a characteristic species of ammonite (A. biplex) of the Portland-rock has been found both in Russia and Poland. In the Himalayas and Central India argillaceous beds occur which contain fossils, which have been regarded as analogous to those of the Lias of Europe.

Bone-bed. At the base of the Lias, and separating the

By Messrs. C. Moore, Binfield, Morris, and Brodie: Medals, vol. ii. p. 549. Annals N. H. 2 ser. vol. xix. p. 56.

† See Dr. Jaeger's work, Ueber die fossilen Reptilien, welche in Würtemberg aufgefunden worden sind. Stuttgard, 1828.

lower shales and limestones from the uppermost Triassic bed beneath, there is a layer of coarse detritus, a few inches thick, commonly known as the Lias Bone-bed,* from the

LIGN. 125.-RESTORED FIGURE OF THE DAPEDIUS OF THE LIAS.

(One-sixth the natural size By M. Agassiz.)

immense quantities of water-worn bones, teeth, and coprolites of fishes, which it contains. It is, in fact, an aggregation of mud, sand, and the debris of fishes and reptiles. Teeth of fishes of the genus Ceratodus (Med. Creat. p. 587), are very frequent in this bed. Aust Cliff, on the Severn, near Westbury, in Somersetshire, is a well-known locality for the fossils of this remarkable deposit. By some geologists this bone-bed is included in the Trias, and by others in the Lias. A similar stratum occupies the same geological position in Germany, and contains organic remains of a like nature.

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Another "bone-bed occurs in the Upper Ludlow series (Geol. Journ. vol. xi. p. 8); and fish-remains are almost as abundant in a portion of the Mountain-limestone (at Clifton and Armagh), and in the Inferior Oolite at Leckhampton Hill. (See Quart. Geol. Journ. vol. vii. p. 211.)

These

Considerable interest is attached to the exact determination of the extent of this "bone-bed," and its associated strata, from England to the Eastern Alps. In the west it appears to have been a comparatively shallow-water deposit; but towards the east it is imbedded in other fossiliferous strata that were evidently deposited in a deeper sea. shelly beds form part of the series termed "Koessen-strata" by the Austrian geologists, and without doubt belong to the Upper Trias. A bone-bed, similar to that underlying the English Lias, occurs near Stuttgard,* and certain sandstone strata there accompanying it are, according to Messrs. Oppel and Suess, the littoral equivalents of the marine "Koessenstrata," so well developed in the Eastern Alps, and characterized to the eastward of Vienna, in the Austrian Salinar district, and even partly in the Alps of Tyrol and Bavaria, by numerous remains of marine animals, especially of Brachiopods and Oysters. In the Vorarlberg, these forms begin to disappear, giving place to Pecten Valoniensis, Cardium Rhæticum, Card. Austriacum, and other pectinibranchiates, indicative of a diminution of the depth of the old sea there. Beyond the overlying strata of more recent date, and along the shores of that primæval sea, these deposits have assumed quite a littoral character; Oysters and Brachiopods having totally disappeared, and the pectinibranchiate molluscs, such as occur in these beds in the Vorarlberg, and some new species, being predominant in the fossil fauna. Hence it is concluded that the "Koessen-beds" are contemporaneous with the ossiferous strata or bone-beds, the existence of which may be traced for a great distance, from the Southwest of Germany to France and England.

*The Stuttgard "bone-bed" is famous for having yielded some minute teeth of a Mammalian animal (Lyell's Manual of Geology, 1855, p. 343, and Supplement, 1857). This will be noticed in the chapter on the Trias, the Stuttgard deposits having been referred to that formation.

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