Yol. 52.] MAMMALIAN REMAINS IN DERWENT RIVER-GRAVELS. 509 



passed down the Trent Valley for some distance to the east of 

 Nottingham. 



In the South of England and in certain areas on the Continent, 

 the flexures of the ' underplight ' seem in all cases to bear a very 

 close relationship to the slopes upon which they occur. According 

 to Mr. Spurrell, it is ■ the result of a steady movement, a flow or push 

 in certain directions in accordance with the slopes on the surface of 

 the land : the amount of slope determining the direction being often 

 very slight/ In the area of the Trent Basin under consideration 

 the phenomena which we are discussing do not, in a large number 

 of cases, bear out the contention that the flexures may result 

 from the flow of surface-deposits down slopes, for they occur on 

 extensive flat areas, and the trend of the furrows and ridges is 

 such, in the majority of instances, as would indicate a movement 

 from the west or thereabouts rather than down the adjoining hill- 

 sides. 



We must, I think, admit that 'trail' and ' underplight' may 

 have been formed under slightly different conditions in different 

 districts, and that the conditions which obtain or have obtained 

 in each district must be deduced from the appearance of the local 

 deposits. 



Otherwise, how are we to explain the fact that indurated masses of 

 gravel such as those at Allenton, Weston, Beeston, Lenton, and Gam- 

 ston, and also other surface-deposits, have been forcibly puckered and 

 bent to depths of from 8 to 12 feet from the surface ? Not on sloping 

 surfaces, be it remembered, but on approximately flat areas of con- 

 siderable extent. That such surface-features are not now being 

 produced may be seen from all the sections of post-Glacial gravel, 

 loam, soil, etc., which have been described. But it is not only the 

 gravels which have been contorted and disturbed in this way. The 

 surface of the older rocks, where it can take and preserve such 

 features, is affected. Sometimes the contortions or waves terminate 

 abruptly at the surface-soil as though they were the remnants of a 

 thicker deposit, the upper portions of which have been removed. 

 That the contortions are not due, in some instances at any rate, to 

 the slipping of the surface-layers by the direct action of gravity 

 is proved by the fact that they often occur on level ground. Indeed, 

 upon the steeper slopes of the area deposits of ' trail ' and contorted 

 surfaces are generally not to be found, for denudation has there 

 acted so energetically that all traces of such surface- action have 

 disappeared. 



We are, therefore, constrained to admit, it seems to me, that the 

 upper terraces covered by the ' trail ' or showing disturbed surfaces 

 aro of Interglacial age. That the Allenton terrace is of Inter- 

 glacial age was stated in a paper read before this Society in 1886, 

 and all subsequent work has tended to confirm me in this opinion. 

 The discovery of Hippopotamus, Rhinoceros, and Elephas in the 

 gravel supports this view rather than militates against it. 



