Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/498

 Crags with those of England after treating of the Norwich Crag. On the latter subject we must make a few observations in reference to that portion of it which extends into Suffolk. I have shown that the Red Crag S. and S.W. of Sudbourne and Iken is separated from that to the northward by a ridge of Coralline Crag, and that the fossils of the Red Crag take then a more littoral character and already present at Aldborough a somewhat intermediate type — the rich fauna of Sutton and Walton having gradually become poorer, though the shells are still all Red-Crag species, and that species of Mactra, Mya, Mytilus, and Cardium have become more common. After passing Aldborough the Crag puts on another type ; the littoral shells, especially Littorina littorea, Mya, and Mactra, largely predominate ; but still, out of 44 species I have found in the pits between Aldborough and Southwold, there are only two which are not found in the Red Crag : — the one, Paludina lenta, being a freshwater and therefore a local shell * ; the other, Astarte borealis, being a shell of northern type, which here first makes its appearance, and whose range may have been restricted by the Thorpe ridge of Coralline Crag.

The Mammalian remains found at Thorpe and Southwold cannot be compared with Red-Crag fossils, which are mostly extraneous. At the same time I would call attention to the occurrence of the teeth of Mastodon in the Coralline Crag of Sutton, in the Red Crag of the same district, and in the Crag at Southwold.

Further the stratigraphical relation of the beds is alike in the two districts. At Chillesford and Iken we find the Chillesford clays and sands overlying the Red Crag ; and in the same way we find at Southwold a crag, which is probably the equivalent of the upper division of the Red Crag, immediately underlying clays which contain similar fossils to those in the Chillesford district. It is possible, also, that in the northern area, as well as in the southern, there are two subdivisions, of which the beds at Wangford and Thorpe may be the lower, whilst those at Bulchamp or Southwold may represent the upper.

In my next communication, I propose tracing the same horizon of the Chillesford Clay into Norfolk, and to show its relation to the Crag-beds of that district and their relation to the Crags of Suffolk.


 * Mr. A. Bell has since found this shell in the Bed Crag at Waldringfield.