DEPOSITS OP THE SUSSEX COAST. 359 



species the circumstance is not surprising. As most of the mollusca 

 included in our list have a considerable climatic range, nothing 

 definite can be said as to the climate they indicate, though the 

 general fades of the collection is certainly not boreal. 



The plants yield mach more satisfactory evidence as to climate, 

 and several of the species in our list have a limited range to the 

 north. In fact the assemblage distinctly points to climatic con- 

 ditions similar to those of England at the present day. The oak, 

 wild-cherry,^ cornel, elder, guelder-rose, and hazel are the only 

 trees yet met with, but of these the cornel does not extend into the 

 North of England. All except one of the plants still live in Sussex ; 

 but Potamogeton trichoides does not now occur in the South of 

 England. 



The lower part of the deposit at West Wittering, though extend- 

 ing below the level of half-tides, is of purely freshwater origin ; but 

 the upper part of the loam contains many estuarine Hydrohice, 

 occasional cockles, and some salt-marsh plants. The incoming of 

 marine species would seem to indicate depression, and perhaps direct 

 continuity with the marine shingle which overlies the fossiliferous 

 deposit. The freshwater and estuarine strata at West Wittering 

 may therefore represent the deposits lying between the purely marine 

 clay at Selsey and the old beach ; but on the other hand it is quite 

 possible that they are older, and that they hel^) to fill the gap be- 

 tween the clay with southern mollusca and the underlying erratic- 

 gravel. In any case, all these fossiliferous deposits are of later date 

 than the erratic-gravel and earlier than the Coombe Eock ; but on 

 the first hypothesis there is a sharp break between the littoral Arctic 

 erratic-gravel and the immediately overlying marine clay with 

 southern shells ; while on the second hypothesis a land period is 

 gradually followed by depression, becoming more and more marked, 

 and then changing again into an upward movement. Which may 

 be the true succession of these minor horizons the evidence is not 

 yet sufficient to decide. 



From what has already been stated it will be clear that on the 

 Sussex coast a deposit of glacial origin is overlain by one yielding a 

 temperate fauna and flora, this latter being without Arctic species, 

 but including a few southern forms. Above these fossiliferous strata 

 lie stony and chalky brick-earth and Coombe Eock, which, if my 

 conclusions are correct, indicate a recurrence of Arctic conditions. 

 The strata yielding evidence of a temperate climate seem therefore 

 to belong to an interglacial or mild episode. 



It may be interesting, before leaving the subject, to sketch the 

 probable correlation of the Pleistocene deposits of the Sussex coast 

 with those of other districts which I have specially studied ; for 

 much additional evidence has recently been obtained, and it now 

 appears that there exists in various parts of this country a charac- 

 teristic interglacial fauna. 



In the Thames Yalley there seems to be a threefold division 



^ The bird-cherry (Prwms padus) is the species found at Selsey ; the common 

 sloe {Primus spiiiosa) has not occurred at either locality. 



Q. J.G. S. No. ]90. 2 b 



