BRITISH POSTGLACIAL &> RECENT DEPOSITS 447 



that a great interval separates the formation of the Fen-beds from 

 the deposition of the Palaeolithic gravels. The old land occupied 

 by Palaeolithic man and his congeners had been worn down by 

 river-action, and cut back for miles by the sea before the oldest 

 of the Pen-beds began to accumulate. There is, in short, an 

 abrupt break between the Palaeolithic deposits and the overlying 

 more recent accumulations, the latter rest upon a highly denuded 

 surface of the former. 



The lowest of the Pen-beds consists, as I have said, of gravel. 

 Unfortunately this gravel appears to contain no marine fossils, 

 the only marine organism detected by Mr. Skertchly being a 

 patch of Flustra on a pebble, which of itself would not be enough 

 to prove that the gravel originated in the sea. He mentions, 

 moreover, that some mammalian remains referable to cervine 

 and bovine animals (Bos primigenius and B. longifrons) have 

 been met with. The occurrence of these does not of course 

 militate against the marine origin of the beds, for the remains 

 in question may have been carried down by streams or washed 

 away from the shore by the tide, and thrown up again by the 

 waves. But, so far as I can learn, the marine nature of the 

 gravels is based chiefly upon the mode of their occurrence. 

 According to Mr. Skertchly they stretch along the margin of 

 the Penland in a pretty continuous band from Sleaford to Peter- 

 borough, at both which points they merge into " valley-gravels," 

 that is to say, gravels of fluviatile origin. They clearly pass 

 under the silt and peat, and as similar gravels are encountered 

 again and again in cuttings, borings, and other sections through- 

 out the Penland, it is inferred that " they form a more or less 

 complete flooring to the basin, just as at the present time the 

 bottom of the Wash is similarly covered." Their intimate con- 

 nection with the silt and peat that overlie them " is shown by 

 the occurrence here and there of patches of those materials in 

 the gravel itself." If we take this fact in connection with the 

 presence of the mammalian remains mentioned above, we arrive 

 at the conclusion that whatever may be the origin of the 

 ". beach-" and " floor-gravels " of the Penland, they cannot belong 



