<;. F. WRIGHT — INTERGLACIAL SHELL-BEDS. 505 



SUPPOSED INTERGLACIAL SHELL-BEDS IX SHROPSHIRE, ENGLAND. 



BY G. FREDERICK WRIGHT. 



Much Light has recently been shed upon the condition of the British isles during 

 the glacial period. The ice which covered so large a portion of them proceeded 

 from tour grand centers. 



(li The first center was Scandinavia. After having moved across the shallow 

 bed of North sea, the ice from this center reached the eastern coast of England 

 from Flamboro head to Yarmouth, and advanced westward to a line connecting 

 Flamboro with London, covering Iloldcrness and a considerable portion of Lincoln. 

 Cambridge, Norfolk and Suffolk counties. The western limit, however, was quite 

 irregular; but Scandinavian bowlders are definitely recognized at various places 

 along the coast and in the interior. North of Bridlington, Scandinavian ice was 

 prevented from reaching the coast by the glacier-shed eastward from Scotland and 

 the northern uplands of England, which partly preoccupied the ground. 



(2) The mountain plateau in northern Wales, of which Arenig, Mawrand Snow- 

 don are the culminating points, was a second center from which ice advanced into 

 England, moving eastward as far as Birmingham, a distance of about 100 miles. 

 This is evidenced by an interesting line of bowlders extending nearly north and 

 south, or nearly at right angles to the movement of the great Welsh glacier. This 

 line of bowlders extends from the vicinity of Litchfield through Birmingham and 

 southward to Bromsgrove. Not only are most of these bowlders definitely trace- 

 able to the Welsh mountains, but near Litchfield some have been found which 

 were brought from the Wrekin, the remnants of a Silurian mountain near "Welling- 

 ton in Shropshire, and about one-third of the distance between Litchfield and 

 Arenig. 



Until quite recently it has been a puzzling circumstance that the glacial deposits 

 of western Staffordshire and northern Shropshire were characterized not by Welsh 

 bowlders but by bowlders that can be clearly traced to the Lake district in England 

 and to the southwestern portion of Scotland. Shap granite from Westmoreland 

 and granite from the Criffel mountains north of Solway firth abound in great 

 numbers in the till of this area. It is in the glacial deposits at Ketley, near Wel- 

 lington, that .Mr. Prentiss Baldwin and myself succeeded in finding the shell-bed 

 from which the accompanying specimens were obtained. As identified for me by 

 Professor Albert A. Wright, the shells are as follows: 



Nassa reticulata ; one specimen. Common in England and France; also fossil from 



the Miocene throughout Europe. 

 Titrritella (Communis ? ) ; many specimens. Smaller than the average hut similar 



in sculpture i Britain has only one species of Turritella) vi/.. Communis). 

 Veiitalium; one specimen (tubular). 

 Lucina ' : one valve. 

 Fragments of ribbed >'<ir<lU<t (possibly Cardium). 



These specimens were near together in a gravelly stratum two or three inches 



t hick, which was underlain by a sandy deposit ■_'■"> or 30 feel thick and overlain by 



from L0 to 15 feet of true till, containing scratched pebbles and small bowlders in 



abundance, the bowlders being all either from the Lake district or from southern 



Scotland. The hit in which this section svas shown has been extensively worked 



