160 S. V. Wood, Jim.— The Post- Glacial Period. 



while the yet newer deposit of Bridlington has two of the first and 

 several of the latter class, and the fauna of all of these three form- 

 ations presents more or less af&nity to that of the Crag, the 

 molluscan remains in all being thoroughly fossilized. The bed, 

 however, which underlies this Sussex clay presents the greatest 

 contrast to these Glacial deposits and to the Crag, as it contains a 

 somewhat numerous molluscan fauna, in fine preservation, which is 

 not only hardly fossilized at all, but consists entirely of species still 

 living, and living, moreover, in contiguous or but little distant seas, 

 and those Southern ones. These living species nearly all occur on 

 our present Southern coast, while of the rest a few are confined to 

 the Lusitanian, and one or two to the Mediterranean coast ; ^ afford- 

 ing pretty clear evidence that at a period not very far back, but an- 

 terior to those ice conditions to which the great blocks occurring in 

 the overlying clay are due, a warmer and more Lusitanian-like sea 

 washed the southern shores of Britain.^ Associated with the mollusca 

 in this bed occur Mammalian remains which present none of those 

 older features attaching to the remains from the Cyrena Brick-earths 

 of the Thames Valley, and of course still less of those attaching to 

 the pre-glacial forest beds of Norfolk ; and which, although neither 

 the Eeindeer nor Musk-ox are among them, are grouped by Mr. 

 Dawkins^ with the ordinary Post-glacial Mammalian fauna of 

 Britain, as distinguished from the Thames Brick-earth group. 



This non-glacial Boulder-clay appears to me to be of even later 

 age than that of Hessle ; and to present evidences of erratic transport 

 requiring much more ice-power, some of the blocks described by 

 Mr. Grodwin-Austen and by Sir Charles Lyell being enormous. 

 Tracing the sequence of events from quite different evidence to the 

 above, I endeavoured to show in the before-mentioned paper that 

 this Sussex clay was formed near the close of those Post-glacial 

 changes to which I trace the present condition of the South and 

 South-east of England;* that is to say, just about the stage when 

 the Weald was completely deserted by the sea, and its drainage 

 reversed into its present direction ; in the gravels of which drain- 



1 A list of 38 species from this deposit is given by Mr. Godwin-Austen in Quart. 

 Journ. Geol. Soc, vol. xiii., p. 50, and as many more have since been obtained by Mr. 

 Alfred Bell. Mr. Godwin- Austen in the same paper also notices the Mammalian 

 remains. 



' In the paper in vol. xxvii. of Quart. Journ. before referred to, I endeavoured to 

 show that subsequent to the formation of the Thames Brick-earths, and prior to the 

 accumulation of this Sussex molluscan deposit, an isthmus joining Kent to France 

 had come into existence, which divided the Lusitanian connected waters of the South 

 of England from those of the North Sea. The marine shells of the Post-glacial 

 gravels of East Anglia have a more northerly character than those of the Sussex bed, 

 though a,s;reeing with them in belonging all to living species, that with a few excep- 

 tions (which occur in contiguous seas) yet survive in British waters. 



3 Quart. Journ. Geol. Soc, vol. xxv., p. 195. See column headed Bracklesham, 



* "We get no evidence of this late Post-glacial ice-action over Essex, Suffolk, and 

 Norfolk, except it be in Mr. Fisher's ' trail,' because, as it appears to me, these counties 

 were then all land, having, in common with all England, at a still later or pre- 

 historic period, undergone that subsidence which is indicated by the submerged 

 forests round our coasts. 



i 



