IN THE THAMES BASIN. IO9 



this remarkable fauna: the one is now a purely Arctic animal^ 

 and the other survives only in Scandinavia. 



Two more voles, the bison and bear, complete the list, while 

 the beaver, urus, reindeer, wolf, and another species of bear, 

 which appear to have lived on into the succeeding Neolithic 

 period, must also be mentioned as interesting members of 

 the Palaeolithic fauna. 



Of the invertebrates there is at least one extinct species of an 

 Ostracod, a Pelecypod, and a Gastropod, while there are several 

 which, though still living on the European mainland, are no 

 longer inhabitants of Britain. 



A complete review of the previous literature relating to the 

 valley drifts of the lower Thames Basin is given by Whitaker in 

 The Geology of London [Memoir Geol. Survey. 1889). This is 

 brought up to date in his Address to the Geologists' Association 

 in 1901. 



A tolerably complete list of the invertebrate remains occurring 

 in these beds will be found in the following papers : — W. J. 

 Lewis- Abbott, " The Sections exposed in the foundations of the 

 New Admiralty Offices," Proc. Geologists' Assoc, xii., 1892. J. P. 

 Johnson and G. White, " Some new Sections in, and contributions 

 to the Fauna of, the River Drift of Ilford," and J. P. Johnson, 

 *' Additions to the Palaeolithic Fauna of the Uphall Brickyard, 

 Ilford," Essex Naturalist xi., 1899-1900. Hinton and 

 Kennard, " Contributions to the Pleistocene Geology of the 

 Thames Valley," Part I., Essex Naturalist, xi., 1900. 

 Kennard and Woodward, " Post-Pliocene Non-Marine MoUusca 

 of the South of England," Proc. Geologists' Assoc, xvii., 190 1 

 (VVartford, Swanscombe, Crayford, and Erith, Green-Street- 

 Green). 



Between the laying down of the last of the valley-drifts and 

 the commencement of the deposition of the next series of 

 deposits — the alluvial flats — a great interval of time must have 

 elapsed, an interval sufficient to permit of the extinction or 

 migration elsewhere of the remarkable assemblage of mammals 

 enumerated above, and to allow of the replacement of the 

 characteristic Palaeolithic implements by others of a totally 

 different type. 



The newest series of fluviatile deposits in the Thames Basin 

 — the beds of clay, mud, and peat which make up the alluvial 



