390 W. SHONE OK THE GLACIAL DEPOSITS OF WEST CHESHIRE. 



occur as striated erratics in the Lower Boulder-clay, the difference, in 

 fact, being that in the Middle Gravels they are rounded and the striae 

 obliterated, while in the Lower Boulder-clay they are angular, sub- 

 angular, polished, and scratched. If it be reasonable to derive the 

 gravels chiefly from this source, it is equally reasonable to derive the 

 Scandinavian shells found in the Middle Sands from the same source. 



Also if we examine the junction between the Upper Boulder-clay 

 and the Middle Sands and Gravels, the latter are very much eroded, 

 so much so that they form dome-like masses with the clay filling up 

 the hollows. The Middle Sands and Gravels contain southern shells ; 

 what, therefore, more likely than that the southern forms, which are 

 very rare in the Upper Boulder-clay, should have been derived from 

 the Middle Sands, and so explain away the apparent inconsistency of 

 such shells as Admete viridula, Natica affinis, and Pleurotoma pyra- 

 midalis occurring in the Upper Boulder-clay of Newton side by side 

 with Area lactea, Venus ehione, and Natica sordida ? 



At the Dawpool Cliffs the River Dee is carrying away the Lower 

 Boulder- clay, and its Scandinavian fauna is being mingled and re- 

 deposited in the delta with the shells of recent species inhabiting 

 the estuary. 



We appear, therefore, to have, as suggested by Prof. Hull, F.R.S., 

 a threefold division of the Glacial drift, although I think it is to be 

 regretted that the terms Lower Boulder-clay, Middle Sands and 

 Gravels, and Upper Boulder-clay should have been chosen to express 

 the phenomena of any particular periods, as we cannot but imagine 

 that clays, sands, and gravels were in course of deposition during 

 all these periods, though of course one or other may have locally 

 predominated at specified intervals. I think that Lower Glacial 

 Drift for Lower Boulder-clay, Interglacial Drift for Middle Sands 

 and Gravels, and Upper Glacial Drift for Upper Boulder-clay would 

 be more comprehensive. 



In conclusion, I believe we have here evidence of a Glacial age, 

 marked in the lowlands of the west coast of England by the marine 

 Lower Boulder-clay ; that it was succeeded by a temperate age, repre- 

 sented by the Interglacial Middle Sands and Gravels*, with their 

 southern Moliusca, as Area lactea, Venus ehione, &c, the boreal forms 

 having been derived from the denudation of the Lower Boulder-clay ; 

 and^ lastly, that in the Upper Boulder-clay we have evidence of a 

 partial return to Glacial conditions like those of the Lower Boulder- 

 clay era, though not so severe, the climate being Scandinavian. 



In the following Tables of Foraminifera and Ostracoda, the 

 species marked 1 in the Liverpool column were found by Mr. T. 

 Mellard Reade, F.G.S., and Mr. David Robertson, F.G.S., not 

 in Turritellce, however, but free in the Boulder-clay ; those marked 

 * in this column were found by me in the sand from within Turri- 

 tellce which were sent to me by Mr. Reade (see Quart. Journ. Geol. 

 Soc. vol. xxx. p. 29). 



* Mr. D. Mackintosh, F.G.S., has recently, on physical grounds, suggested 

 the Interglacial character of the Middle Sands and Gravels. I rest my opinion, 

 however, more upon -the southern fauna. 



