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been derived from those formed at the time of the Coralline

Crag. (See p. 285.)

In the Suffolk Bone-bed are found rounded masses and nodules of sandstone termed Box stones, which sometimes contain fossils. Mr. Lankester has remarked on their resemblance to the Lenham sandstones. (See p. 264.)

The Coralline Crag is well shown in the neighbourhood of Woodbridge, Aldborough, and Orford, at Sutton, Ramsholt, Sudbourne, Broom Hill, Gedgrave, &c.

Amongst the fossils are Cypraea Europaea, Voluta Lamberti, Turritella incrassata, Fusus consocialis, F. gracilis, Scalaria clathratula, Natica, Calyptræa Chinensis, Fissurella Græca, Anomia ephippium, Ostrea edulis, Pecten opercularis, P. maximus, P. Gerardii, Pinna pectinata, Pectunculus glycimeris, Nucula nucleus, Lucina borealis, Diplodonta rotundata, Cardita senilis, C. scala: is, Astarte Omalii, A. gracilis, Cyprina Islandica, C. rustica, Venus casina, Panopœa Faujasii, Terebratula grandis, Balanus crenatus, Fascicularia, Cladocora, Turbinolia, Echinus Woodwardi, Heteropora pustulosa, Cellepora edax, &c.

Mr. Wood considers that the Coralline Crag was deposited in the sea at no depth greater than 300 feet.

RED CRAG.

This deposit consists generally of dark red shelly sand, often exhibiting false-bedding or oblique lamination, and having a thickness of about 25 feet. Sometimes the colour is yellow, brown or grey. Seams of laminated clay are occasionally met with. Mr. S. V. Wood, jun., has, however, shown that the deposit is structurally divisible into five stages, of which the 1st, 2nd, 3rd, and 4th (counting upwards) were not deposited under water; but from their being regularly laminated, at angles varying between 25° and 35°, and possessing (with the exception of the 2nd) an unvarying direction

in every stage, he regards them as the result of a process of 'beaching up,' by which was formed a reef extending from the river Alde on the north, to the southern extremity of the deposit in Essex. Of these four stages, the 4th is the most constant and important, the 1st, 2nd, and 3rd being frequently either concealed by, or destroyed during the formation of, the succeeding stages. At Walton-on- Naze alone do any of the four lower stages contain evidence of being a subaqueous deposit; there the 1st stage is so, but it is covered by two reef stages, and these again by the 5th stage.

The 5th stage is invariably horizontal, and contains evidence of having been formed under water. This stage is developed in such a way as to show that it was formed in channels eroded in the older reef, and it is at its base that the coprolite workings occur.

Owing, however, to the probable reconstruction or reaccumulation of different stages, Mr. Wood considers it impossible to separate the Red Crag in general, into all those chronological divisions of it that may exist, but there are three divisions that are very clearly indicated:

3. Scrobicularia Crag Largely made up of Tellina prætenuis, and T. obliqua, with also Scrobicularia plana.

2. Deben, Orwell, and Butley Red Crag, with northern forms of mollusca predominating.

1. Walton Grey and Red Crag, containing many species characteristic of the Coralline Crag.

The Scrobicularia Crag comprises beds which gradually lose both the red colour and the oblique bedding as we ascend the section, and become horizontal in the upper layers.

The Red Crag is well shown at Walton-on-the-Naze, Sutton, Ramsholt, Trimley, Bawdsey, Butley, Hollesley, &c.

Near Aldborough and at Park Farm, Tattingstone near Ipswich, the Red Crag may be seen in section superimposed upon the Coralline Crag.

A bed of phosphatic nodules called 'coprolites' often occurs at the base of the Red Crag, and with it are found fragments of septaria from the London Clay, Chalk flints, Greensand chert, rolled or water-worn bones and teeth of Cetacea, Sharks (Carcharodon megalodon), &c. According to Mr. Prestwich seams of phosphatic nodules, or dispersed nodules, may be found through the whole of the Red Crag; and all of them were probably derived from the Coralline Crag. Among the Cetacean bones are the earbones of Whales, while other derived fossils are Crustacea from the London Clay.1

The 'coprolites' yield from 45 to 60 per cent. of Phosphate of Lime: they have been worked near Sutton, Boyton, Butley, Trimley, Bawdsey, Shottisham, &c. The beds are however becoming exhausted. (See p. 244.)

The question whether some of the forms characteristic of the Coralline Crag may not be derived from older deposits, is important, but, according to Mr. Wood, it is a still more complicated problem whether or not the fossils of the Red Crag in its various stages have a derived origin.

The fossils of the Red Crag include the Trophon (Fusus) antiquum, of which the sinistral or left-sided form (var. contrarium), according to Mr. Wood, is found in the Walton Crag, while the dextral form abounds in the rest of the Red Crag. Other fossils are Pecten opercularis, Pectunculus glycimeris, Mactra arcuata, M. ovalis, Tellina obliqua, Cardium edule, C. angustatum, Mytilus edulis, Nassa reticosa, Buccinum tenerum, B. undatum, Natica catena, N. multipunctata, Purpura tetragona, P. lapillus, Turritella incrassata, &c.

In the famous sections at Chillesford the Scrobicularia Crag rests upon the Red Crag (of Butley), and is directly

1 Many fossil bones and teeth washed out of the Red Crag may be picked up on the beach at Harwich and Walton.

overlaid by the Chillesford Beds. It was these sections, first noticed by Mr. Prestwich, which led to the relations of the Norwich (Fluvio-marine) Crag and Red Crag being determined the former being the equivalent of the higher portion of the latter. (See p. 289.)

From a careful study of the Crag district Mr. S. V. Wood, jun., concludes that the northern part of the Red Crag area continued to receive accumulations up to and during the time when the Fluvio-marine Crag was deposited; these beds were overlaid conformably by the Chillesford Beds, while in the southern part of the Red Crag area, as at Walton-on-theNaze, the Chillesford Beds overlapped and rested unconformably upon the lower portion of the Red Crag.

NORWICH CRAG SERIES.

LAMINATED SERIES. (Gunn.)

The seams of shelly sand or crag which occur in Norfolk are of a very impersistent character, but the researches of the Messrs. Wood, of Mr. F. W. Harmer, and of Mr. J. E. Taylor, have demonstrated that there are at least three horizons of crag which are termed the Fluvio-marine Crag or Norwich Crag proper, the Chillesford Crag, and the Bure Valley Crag; and that these are marked by some differences in the assemblage of mollusca.

The formation, to which the term 'Norwich Crag series' seems applicable, comprises a variable set of beds, of sands, laminated clays, and shingle, with in places seams of shells, which rest on the Chalk, attain a thickness of about 30 feet, and are overlaid by the Glacial deposits.

[In this section No. 5 is the representative of the Bure Valley Beds, No. 4 embraces the Chillesford Beds, and Nos. 2 and 3 include the Fluvio-marine Crag. The beds are very variable, and attain a total thickness of about 20 feet. The disturbance in the Chalk so conspicuous in 1868, is not very marked in the portions of Chalk now exposed (1876).] FIG. 21.-Chalk pit at Whitlingham, near Norwich.

[graphic]

3. Sand and gravel, false-bedded.
2. Shell-bed and large flints.

5. Pebbly gravel and sand.
4. Laminated clay and shelly seam.

1. Chalk (disturbed).

Fluvio-marine Crag.1

The Fluvio-marine Crag consists of buff-coloured shelly sands and shingle, often false-bedded, having a thickness of

This is by no means a good name, as the Chillesford Beds are in places fluvio-marine, and the Bure Valley Beds contain some freshwater molluscs.

5.

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