The Bovey Beds comprise two well-marked divisions, the lignite-beds which are developed at Bovey Tracey, and the clay-beds which are so largely worked near Kingsteignton and Newton Abbot.

The exact relations between these two divisions cannot readily be ascertained, for the lignite-beds are cut off by a fault (determined by Mr. Divett), where the vertical displacement is estimated at 100 feet; but so far as I could determine from personal examination the lignites form the upper series above the clays.

The beds opened up at Bovey (according to Mr. Pengelly) are as follows:

A boring made east of the fault showed upwards of 80 feet of sands and clays, with some coaly beds in the lower portion.

The clay-beds of Kingsteignton are about 40 feet in thickness, resting on sand, and containing occasional sandy beds.

The total thickness of the Bovey deposit can only be conjectured as between 200 and 300 feet.

The beds extend over a considerable tract of low-lying heath-land bounded by ranges of hills. The physical and palæontological evidence points to the deposit having been formed in a fresh-water lake, which probably extended from

Bovey Tracey to Kingskerswell, without being open towards Teignmouth. The purely sedimentary matter was evidently derived from the waste of the Greensand and of the granitie rocks of Dartmoor: the clays being due to the decomposition of the felspars, and the quartzose sands being the relics of the harder material. (See fig. 12, p. 110.)

It has been conjectured that the Lower Bagshot beds of Poole were similarly derived, and although there is great similarity in the general character of these beds and those of Bovey, yet it appears that the plant-remains of the two deposits are very distinct.

From Dr. Heer's investigations it seems that the woods. covering the slopes which surrounded the old lake consisted mainly of a huge coniferous tree (Sequoia Coutssia), whose figure resembled in all probability its highly admired cousin, the Sequoia (Wellingtonia) gigantea of California. The leafy trees of most frequent occurrence were the cinnamons and an evergreen oak like those which now are seen in Mexico. Species of evergreen fig were rarer. The trees of the ancient forest were evidently festooned with vines, beside which the prickly Rotang-palm twined its snake-like form. In the shade of the forest throve numerous ferns; one species of Pecopteris seems to have formed trees of imposing grandeur, while on the surface of the lake were expanded leaves of the water-lily.1

The lignite, which has been used extensively for fuel, is very little employed now, as it gives off a sulphurous smell when burning.

The clay-beds yield excellent pipe and potters'-clay. The best clay is shipped at Teignmouth, whence it is sometimes termed 'Teignmouth Clay.' According to Mr. Hunt's Statistics above 42,000 tons were sent from the port of Teignmouth in 1865. The mode of raising the clay is extremely

1 Phil. Trans., Part II. 1862.

simple the gravel head is removed, and a large rectangular pit is sunk, which is supported by wood. The workmen cut out the clay in cubical lumps weighing about 30 lbs. each, and fling them from stage to stage by means of a pointed staff; it is then carried to the clay cellars, and when properly dried sent to the potters.

Iron-pyrites is abundant in the lignite-beds, and from its presence spontaneous combustion sometimes takes place after heavy rain in the refuse-heaps.

The clays are employed for whitening stones, &c.; they have also been used in the manufacture of alum.

PLIOCENE.

The Pliocene deposits of England, so far as known, occur in the Eastern Counties, and are recognized not only by position, but by the large per-centage of recent species of Mollusea which they contain. Their exact relations, however, to the Miocene period are not by any means definite, and some authorities have classed the lowermost division of the series-the Coralline Crag-as Miocene; but this seems to be an unnecessary complication in classification, and certainly the Crag deposits are closely united as well in their physical as in their palaeontological characters.

Certain ferruginous sands containing casts of molluscs which occur on the Chalk in Kent and Surrey, were at one time considered as Crag, but their age is extremely doubtful, and it is uncertain whether they all belong to one period. (See p. 264.)

Some of the pebbly gravels which cap the Tertiary hills

1 Sometimes spelt Pleiocene. The term Icenian was proposed for the Pliocene strata, because their order of succession was first determined in the Eastern Counties. (S. P. Woodward.)

in Hertfordshire and elsewhere may, as suggested by Prof. Hughes, be of Pliocene age, but this view depends very much upon the position of the boundary-line taken between Pliocene and Glacial deposits. (See p. 312.)

CRAG.

The deposits of shelly sand called 'Crag' which occur on the eastern borders of Norfolk, Suffolk, and Essex, have long been known, but for the minute description and identification of their Molluscan remains we are indebted to Mr. Searles Wood, sen., while we owe our knowledge of the detailed structure of the deposits very largely to Mr. Wood, jun.

6

Forty years ago, however (1835), Mr. Charlesworth gave the first good account of the Crags in Suffolk, and he then proposed the terms Red Crag' and 'Coralline Crag' to distinguish them from one another, and from the Norfolk or Norwich Crag, to which he subsequently applied the term 'Mammaliferous Crag.'

Since this date the labours of Messrs. S. V. Wood, jun., F. W. Harmer, the Rev. O. Fisher, Prestwich, and some others, have added greatly to our knowledge of the Pliocene strata, and the following stratigraphical divisions are now generally adopted-the upper part of the Red Crag being considered as the representative of the Fluvio-marine Crag :-5. Bure Valley Beds.1 4. Chillesford Beds. 3. Fluvio-marine Crag. 2. Red Crag.

1. Coralline Crag.

Norwich Crag or
Laminated Series

(Newer Pliocene.)

} (Older Pliocene.)

1 Classed as Lower Glacial by Wood and Harmer. (See p. 308.)

CORALLINE CRAG.

SUFFOLK CRAG, WHITE CRAG, or BRYOZOAN CRAG.1

The Coralline Crag consists of a series of calcareous shelly sands, sometimes marly, and having a thickness of from 40 to 60 feet.

The following general divisions are abbreviated from those given by Mr. Prestwich :--

7. Sand and comminuted shells, with remains of Bryozoa, sometimes forming a soft building-stone, showing much false-bedding.

6. Sand with small shells and seams of comminuted shell.

5. Sands with numerous Bryozoa, often in the original position of growth, and containing also small shells and Echini.

4. Comminuted shells, large entire or double shells, and bands of limestone.

3. Marly beds with well-preserved shells.

2. Comminuted shell-beds with Cetacean remains and Bryozoa.

1. Bed with Phosphatic nodules, called 'Coprolites,' and mammalian remains,-called the Suffolk Bone-bed.

The Suffolk bone-bed, or Coprolite bed,' has been described by Mr. E. Ray Lankester as being a bed from half a foot to three feet in thickness, and lying upon the London Clay in Suffolk wherever the Red Crag or the Coralline Crag is found. It is composed of rounded phosphatic nodules called coprolites,' and water-worn teeth and bones of Mastodon, Rhinoceros, Tapir, Bear, Whale, and Shark. Mr. Lankester considers that the Cetacean remains were derived from the older crag-deposit found in Belgium, and known as the Diestien or Black-crag.2

The beds at the base of the Red Crag may, however, have

1 The term Bryozoan Crag was proposed, because there are few Corals in this Crag, the forms which led to the proposal of the term Coralline being Bryozoa or Polyzoa.

2 Mr. Colchester considers the 'Coprolite' bed to be the débris of a bed intermediate in age between the London Clay and the Coralline Crag.