THE PLEISTOCENE SERIES 643 



ni.u 1> containing bones of mammalia, freshwater shells, and reinnin- 

 of plants ; these are overlain by brownish clay or brick-earth 

 enclosing flint UMplrim-nta of a Palaeolithic type. The plants 

 include leaves of Salix polaris, S. myrtinites, and Betula nana 

 (all Aivtir forms), with others of more southern cliaracter, but the 

 flora somewhat resembles that of modern Iceland. 28 



Similar deposits occur in a broad depression south of Hitchin 

 in Herts, and consist of alluvial marls and silts resting on boulder- 

 clay and overlain by brick-earth with implements of Mesolithic 

 tyin'.- 4 The flora, however, does not include the Arctic species, 

 .mil indicates a more temperate climate. 



Cave Deposits. The origin of caves and the formation of 

 the deposits found in them is explained in most books on Physical 

 Geology. Many such caves have now been explored in England 

 and Wales ; some of them have served as dens for bears or for 



Fig. 210. SECTION ACROSS THE TRUMPDfOTON GRAVELS. Distance 2 miles. 



a. Lowest terrace. d. Chalk marl 



6. Second terrace. e. Gault. 



c. Highest terrace. /. Alluvium. 



hyaenas, and the bones of other animals belong to carcases which 

 have been dragged in by these creatures. At other times they have 

 served as shelters for man, whose occupation of them is proved by 

 the frequent occurrence of stone implements Palaeolithic in the 

 lower beds, and sometimes Neolithic in the higher. The caves of 

 ( 'iv.-wt-Jl Crags in the Magnesian limestone on the borders of Derby 

 and Notts afford good examples of such deposits. 25 In Robin Hood 

 Cave the beds found were : 



Feet. 



5. Stalagmite united to the roof 1 to 2 



4. Breccia with bones and implements . . . . . to 3 



3. Cave earth with bones and implements . . . . 2 to 4 



2. Red clayey sand with bones . . . . . . 2 to 4 



1. Light-coloured sand with blocks of limestone fallen from 



the roof 2 



The lowest sand yielded no organic remains, but the red sand 

 contained bones of many animals, all of them scored with the teeth- 



