Trophon clathratum ( = T. truncatus = Fusus 
Bamffius) . 
Pleurotoma (Mangelia) rufa. 
P. turricula. 
Turrit ella terebra. 
Artemis exoleta. 
Astarte borealis. 
Cardium edule. 
C. echinatum. 
Mytilus edulis. 
Ostrea edulis, young. 
Tellina balthica. 
If we follow these beds round the eastern flanks of the 
Welsh hills to the south, we can trace them now in continuous 
sheets of sand and gravel, now in detached terraces and patches 
down to the basin of the Severn. They are probably the 
beds mentioned by Murchison* and by Trimmer.! 
If we examine them, following the excellent work of Mr. 
Shone, { of the Chester Society of Natural Science, as they 
stretch at lower levels across the estuary of the Dee, and 
here and there along the western coast of Lancashire, 
towards the Lake District, we find just the same evidence, — 
re-sorted drift, with shells, some showing affinity with northern 
types, but most of them like recent temperate forms. Before 
we leave the north and western shore of this primaeval sea, 
let us consider what the obvious simple explanation of the 
whole may be. 
When the lofty ice-clad land began to be submerged, the 
sea lifted and floated off the ice that came down to its 
level in glaciers, so all the lower lands beyond the moun- 
tains were still loaded with iceberg debris , which could not 
have come if one ice-sheet prevailed over all the mountains. 
This debris , too, was different, according as the ice from 
Scandinavia, Scotland, or North Wales prevailed. As still the 
land went down, the climate changed, and the ice receded, no 
longer reaching the sea level, and so no longer bergs floated 
from the ice-foot with their load to distant spots. But on the 
flanks of hills the accumulated debris of the earlier times was 
eaten into by the waves, as on that sinking land successive 
parts were brought within their action. Then, as now, the 
shingle travelled round the coast from bay to bay, and any 
* Sil. Syst. f Proc. Geol. Soc ., vol. ii., p. 200. 
J Quart Journ. Geol. Soc., vol. xxxiv., p. 383. 
