THE POST- PLIOCENE. 27 



by the tidal currents sweeping up the coast, or by tlie Arctic current 

 from the nortli, and deposited on the surface of Prince Edward Island, 

 then a shallow sand-bank. The sands with sea-shells probably be- 

 longed to this period, or perhaps to the later part of it, when the 

 land was gradually rising. Frince Edward Island thus ajipcars to 

 have received boulders from both sides of the Gulf of St Lawrence 

 during the later Post-pliocene period; but the greater number from 

 the south side, perhaps because nearer to it. It thus furnishes a 

 remarkable illustration of the transport of travelled stones at this period 

 in different directions ; and in the comparative absence of travelled 

 stones in the lower boulder clay ; it furnishes a similar illustration of 

 the homogeneous and untravelled character of that deposit, in circum- 

 stances where the theory of floating ice serves to account for it at 

 least as well as that of land ice, and, in my judgment, greatly better. 



Subdivisions of the Pleistocene Deposits. — In Chapter V., and in my 

 Memoirs on the Pleistocene of the St Lawrence Valley, I have proposed 

 a threefold division of these beds into Boulder clay., Lecla clay., and 

 Saxicava sand and gravel, to which may be added the old peaty 

 deposit observed under the boulder clay in Cape Breton. Mr 

 Matthew has since recognised in ^'cw Brunswick certain beds only 

 locally developed in the St Lawrence Valley, and whicli I have been 

 hitherto disposed to regard as depending on the action of streams 

 from the land or littoral agencies, but which he regards as marine 

 deposits. They arc gravels and sands underlying the boulder clay, 

 and as yet destitute of fossils. lie suggests for these the name 

 " Syrtensian" beds, proposed by Packard for the fauna of the Great 

 Bank deposits of the Newfoundland and New England coasts, but tlie 

 application of whicli to the beds in question depends on a theory 

 of their origin not yet certainly established. He also recognises, as I 

 have done in the St Lawrence Valley, a lower and upper member of the 

 Leda clay — the latter being equivalent in its fossils to the Uddevalla 

 beds of Sweden. The complete series of Pleistocene beds in Acadia 

 and Canada would tlius stand as follows, in aseemling order, though 

 it is to be observed that tlie wliole scries is not to be found 

 developed at any one place : — 



(«.) Peaty terrestrial surface anterior to boulder clay. 



[b.) Lower stratified gravels — (Syrtensian deposits of ^Matthew). 



(c.) Boulder clay and unstratified sands with boulders. Fauna, 



Avhcn present, extremely Arctic. 

 [d.) Lower Leda clay, with a limited number of highly Arctic shells, 



sucli as are now found only in permanently ico-laden seas. 

 (e.) Upper Leda clay ami sand, or Uddevalla beds, holding many 



