196 Mrs. McKenny Hughes—Pleistocene Mollusca. 
Barnwell Station; here the gravel is seen resting on the Gault, 
which is in places troughed in such a manner as to suggest the beds 
of ancient streams (see Section Fig. 2). 
There seems to be one such old channel here at the margin of the 
gravel, running parallel to the present river-valley. 0, c, d, and e 
of the section are river deposits which have filled it up; some of 
the looping is perhaps caused or increased by the decomposition of 
underlying chalky beds. The channel here and there cuts just into 
the top of the Gault, and patches of the overlying Chalk-marl and 
Phosphate Bed are left; the banks seem to have fallen in in places, 
and the gravel has sunk into the puddled surface of the clay, so that 
the Gault, Phosphate Bed and gravel are sometimes kneaded up 
together in the most irregular manner. The gravel (c) thickens out 
to the west, and falling over the slope to the lower ground forms the 
main mass of the bank next Stourbridge Common, and corresponds 
to the gravel near the Holy Well at Barnwell Abbey, which in like 
manner lies on the west slope of a bank of Gault (see Fig. 3). 
This western portion, both here and at Barnwell Abbey, forms 
the margin of a lower terrace, which being directly derived from the 
higher level gravels, can hardly be distinguished from them on the 
ground. The deposit in which the shells occur at Barnwell Station 
(e) is older than this flanking gravel, as, at Barnwell Abbey, the 
shell-bearing strata are older than the gravels west of the Gault 
ridge, and between it and the river. When, however, we have to 
consider the relative age of the shell-beds at Barnwell Station and 
those at Barnwell Abbey, we find that the question is more complex. 
The lie of the ground seems to point to their being part of the same 
mass, but the character of the deposits seems to indicate that though 
they belong to approximately the same age, they were nevertheless 
laid down under somewhat different conditions. 
With the interruption of the lower level gravels of the Cam 
Valley, described by Mr. Jukes-Browne, we find beds similar to 
Fig. 4.—Section South of Grantchester. 
Scale—10 feet to 1 inch. 
a, Surface soil and rusty gravel from which the Chalk has been dissolved out ; 
6, Chalky gravel and marl with pans of peaty silt and bands full of land and 
freshwater shells ; c, Chalk-marl and Phosphate Bed; d, Gault. 
