4. Mammaliferous crag of Norfolk and Suffolk, hitherto confounded with "red crag," containing about 80 species of shells; proportion of extinct species undecided. (Bramerton, near Norwich; Southwold and Thorpe in Suffolk.)
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| SECTION II. | Beds in which few traces of terrestrial mammalia have yet been discovered:—
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| 5. Red crag. (It contains mastodon, &c.) | |
| 6. Coralline crag. | |
| 7. London clay. (It contains quadrumana, &c.) | |
| 8. Plastic clay. |
Modern Lacustrine Deposits.
Some small lakes are situated at this day, and many were in former times, so as to receive no considerable river, but many small runlets from the adjacent slopes. Under ordinary circumstances, the running streams throw into lakes only carbonate of lime, and other dissolved or suspended matters, which may be diffused with great equality in the water, and at length settle on the bottom in one or more layers. In times of abundant rain, coarser sediments are carried into such lakes from more numerous points of the margin, and thus the whole lake is filled toward the edges by narrow concentric sloping layers of sand and gravel (s), which are intermixed with layers of finer clay or marly substance (c), as in the diagram No. 80.; which also shows,
above several deposits of coarse and fine earthy mate-
