﻿S. V. Woocl,jun. — American and British Surface- Geology. 495 



these marine clays belong to a later glaciation than that to which 

 the Erie clay owes its origin ; because I cannot, as I have already 

 observed, conceive that with such vast erosive power as is attributed 

 to glacier-ice any deposits of prior Glacial age could survive its 

 destructive agency, so far as it extended. In the case of the older 

 Glacial beds of East Anglia they remain undestroyed, it seems to 

 me, only so far as the subsequent ice giving rise to the Middle and 

 Upper Glacial formation did not extend. The depth of the water 

 under which the Lower Glacial of East Anglia accumulated renders 

 it difficult to conceive that this formation did not extend north and 

 west of the limits to which it is now restricted ; and it must have 

 extended either in a marine or terrestrial form as far northwards 

 as the ice to which it owed its origin wasted back or deflected ; so 

 that when we combine the absence of any formation representing it 

 in the North of England with the Crag-like character of the mollusca 

 of its basement sands, it seems but reasonable to regard this earlier 

 part of the Glacial series as having been largely destroyed by the 

 subsequent advance upon it of the ice.^ Now there is an absence 

 from the marine clays of the Lower St. Lawrence basin, and of the 

 Atlantic coast, of any species of mollusca but such as still occur in 

 a living state either in the Atlantic or in the Arctic sea immediately 

 north of it,^ while there are Crag forms in the English older Glacial 

 beds, which are not known as living at all ; and others, whicli, 

 if living, are only represented by species known as such in 

 the North Pacific ; and two of these, as, e.g. Nucula CobboJdice, and 

 Tellina ohliqua, range in our Upper Glacial clay up to what I regard 

 as about the middle place in its horizontal accumulation, viz. 

 Dimlington Cliff base, and Bridlington. This leads me to think 

 that the marine clays of the Lower St. Lawrence and of the Atlantic 

 coast were deposited during the time of the later or minor ice-sheet 

 which gave rise to the beds 3a of Ohio. Mr. Geikie also in his 

 second edition refers these clays to the later part of the Glacial 

 period as defined by him, which corresponds with what I call post- 

 Glacial. 



Besides the beds above described, and those yet to be mentioned 

 under the number 4, there is the great Bluff formation or Loess of 

 the Mississippi valley, described by Sir Charles Lyell in the succes- 

 sive editions of his well-known works, and in which at Natchez be 

 mentions the occurrence of a human pelvis. 



This formation Prof. Newberry regards as the silt brought down 

 by the rivers which form the Mississippi drainage system when in 

 flood, and spread out over the great valley as the sea by the eleva- 

 tion of the continent receded from it, the chief contributor being the 

 Missouri with its affluents. There is, he says, evidence that the 

 lower part of the valley near New Orleans was depressed nearly 



1 The line up to whicli this formation, and also the Middle Glacial and earliest 

 part of the Upper, have heen destroyed by the subsequent ice is defined in a note to 

 the sequel of this paper. 



2 This, at least, is my impression, from the works to which I have had access. If 

 the facts are otherwise, then my argument to that extent fails. 



