Vol.52.] MAMMALIAN REMAINS IN DERWENT RIVER-GRAVELS. 503 



near Allenton on the inside boundary : a large number of limestone- 

 pebbles having been found in a deep ditch south-west of Boulton. 

 Under the nearly impervious covering of clay at Allenton, limestone- 

 pebbles are numerous and fresh. Indeed, except as regards its 

 weathered, disturbed, and stained condition, there is no marked 

 difference between the terrace-gravel and the gravel of the lower 

 alluvia plain. 



Fig. 4. — Interglacial river-gravel, Alvaston, near Derby. 



I have already stated the fact that the brook which drains the 

 southern portion of the terrace, and debouches upon the modern 

 alluvial plain of the Derwent near Thurlston, rises near Allenton : 

 the contour-lines on the south-easterly portion of the map (fig. 2) 

 being deflected when they reach the upper end of the trough. The 

 section (fig. 3) shows this trough in the gravel filled with sand and 

 clay. It runs approximately from N.W. to S.E., and was proved 

 to exist by several borings which entered gravel a few yards to the 

 north-east of the spot where the bones were found. This is con- 

 firmed by Mr. Allen, who informed us that wells sunk to the N.E. 

 do not enter the bone-bed, but pass directly into the lower gravel, 

 while wells to the S.W. enter red marl. 



South-east of Allenton the soft trough-deposits have been denuded, 

 and a depression has been formed along which the stream runs. It 

 seems to have been a deserted loop of the Derwent, formed when 

 the river ran at the level of the terrace. 



In favour of the view that the dark sand and fine blue clay are 

 of the same age as the terrace, the following additional considerations 

 may be urged. In the first place, the limestone-pebbles found 

 beneath the trough-deposits are in a better state of preservation 

 than they are near the edge of the terrace, and appear to have been 



Q. J. G. S. No. 207. 2 m 



