4 G. F. Wriyht — -Theory of an 



Macclesfield there-is an entire absence upon its flanks botli of 

 glacial deposits and of beach lines. 4th. The shell-beds are 

 strictly confined not only to the area which was demonstrably 

 covered by glacial ice, but to those more limited areas which 

 were reached by ice that is known to have moved in its 

 way over shallow sea bottoms. 5th. The assemblage of shells 

 is not such as could have occurred in one place in the ordinary 

 course of nature. There are associated together in these de- 

 posits cold-water forms with warm-water forms, rock-haunting 

 species with sand- or mud-loving species, and in no case has a 

 shell been found in these beds with its valves in apposition. 



An interesting illustration of this latter point is brought out 

 in Mr. Kendall's paper " On the Occurrence of Nassa serrata 

 Brocchi, in the Glacial Drift of the Northern Shore, Ramsey, 

 Isle of Man." This mollusk is now characteristic of the Medi- 

 terranean Sea, and cannot endure even the present temperate 

 climate of the Irish Channel, yet specimens of it are found in 

 the glacial deposits on the Isle of Man. It is in the highest 

 degree improbable that this mollusk could have lived where it 

 was found under any conditions that have been supposed to exist 

 since the close of the Tertiary period. The theory that it was 

 transported from the remains of Pliocene beds on the shallow 

 bottom of the Irish Sea is certainly the most natural if only 

 one can grant that it is conceivable. Other shells found in the 

 glacial deposits in Northwestern England and Wales almost as 

 much out of place are Cytherea chione L., Mitra sp., and 

 Turritella triplicates Brocchi. It is worthy of note, also, that 

 Prof. Edward Forbes early called attention to the fragmentary 

 condition of the shells in the beds of the northwest of England, 

 and to their general distribution through the till. Speaking 

 of the Moel Tryfaen shells he says: "I have lately examined 

 them carefully with a view to see whether they indicate an 

 ancient coast-line or beach, or an ancient sea-bottom. But 

 they cannot be regarded as indicating either, being a confused 

 mixture of fragments of species from all depths, both littoral 

 and such as invariably live at a depth of many fathoms. . . 

 Such deep- and shallow-water species mingled could at no time 

 have lived together, or been thrown upon one shore."* 



During a visit this summer to Ketley, near Wellington in 

 Shropshire, in company with Dr. Crosskey, Mr. Martin, and 

 Prentiss .Baldwin, we were fortunate enough to discover an 

 unusually large collection of nearly perfect shells in the inter- 

 stratified glacial deposits of that place. We could not indeed 

 determine that there was till underneath the sand (which was 

 here twenty-five or thirty feet at least in thickness), but there 



* Memoirs, Geological Survey, vol. i, p. 384 ; quoted by Dugald Bell. 



