“These in descending order are:
“1. Post-glacial sands, gravels, etc.
“2. Glacial series.
“3. The ‘Forest Bed’ and associated marine deposits.
“4. Chillesford clay and sand.
“5. The many successive stages of the Red Crag. (The Norwich Crag is a local variation of the upper part of the Red Crag.)
“6. The Coralline Crag.
“The fossils preserved in these deposits, apart from the physical indications, exhibit the climatal changes which accompanied their deposition. The Coralline Crag contains a fauna consisting mainly of species which now range to the Mediterranean, many of them being restricted to the warm southern waters. Associated with these are a few boreal forms, but they are represented in general by few individuals. Here and there in the deposits of this age far-travelled stones are to be found, but they are always accounted great rarities.
“The Red Crag consists of an irregular assemblage of beaches and sand-banks of widely different ages, but their sequence can be made out with ease by a study of the fauna. In the oldest deposits, Mediterranean species are very numerous, while the boreal forms are comparatively rare; but in successive later deposits the proportions are very gradually reversed, and from the overlying Chillesford series the Mediterranean species are practically absent. The physical indications run pari passu with the paleontological, and in the newer beds of the Red Crag far-travelled stones are common.
“In the Forest Bed series there is a marine band—the Leda myalis bed—which contains an almost arctic assemblage of shells; while at about the same horizon plant remains have been found, including such high northern species as Salix polaris and Betula nana.