1870. ] LLOYD—-AYON AND SEVERN VALLEYS. oe 
down the valley of the Avon, at a height of from 20 to 50 feet 
above its present course, and that the gravel previously brought 
into the district by marine currents was remodified by the river- 
stream, and mixed up with the remains of the mammalia and mol- 
lusca which tenanted its banks or its waters” (see Brit. Assoc. Re- 
ports, vol. vi. Sections, p. 64). I submit that the above view may 
be extended to other portions of the same area. Thus there appears 
to be evidence of :— 
(1) A former time when the main valleys of the Avon and Severn 
existed pretty much in the state in which we now find them. 
(2) A period when the greater portion of them were filled up, to 
a considerable extent, with the drifts of the upper and lower series, 
during the latter part of which, perhaps when the land was emer- 
ging, an arm of the sea occupied the lower portions of the Avon and 
Severn valleys, reaching probably to a height of from 200 to 300 
feet, or thereabouts, above the present sea-level, at which time, we 
may suppose, with Sir R. Murchison, that the mammalian remains 
found near Worcester were washed into the ancient estuary from 
the neighbouring land-surfaces by sudden and local floods, and 
imbedded along with marine shells in the beds of sand and gravel, 
the negative evidence of the absence of freshwater shells, coupled 
with the occurrence of marine shells, preventing our having recourse 
to fluviatile agency for their transport. At the same time proba- 
bly, the local drift at the base of Bredon Hill, containing marine 
shells and remains of mammalia, was deposited. 
Towards the close of this period, and probably after the state of 
things just described had passed away, the sea having receded to 
about its present position by a further elevation of the land, and 
the action of the retiring waters having perhaps scooped out chan- 
nels in the marine deposits in parts of the valleys, leaving eroded 
surfaces of clay and marl, upon which is found so large a percent- 
age of the mammalian remains, the ancient river Avon brought 
down detritus derived from the adjacent beds of marine gravel, 
redepositing it in stratified beds along with land and freshwater 
shells over the surface of the clay; whilst the river Severn, in its 
turn, may have borne the detrital matter brought down from the 
marine deposits of the valley, along its comparatively straight 
course, towards the sea. This process of removal and redeposition 
may be supposed to have gone on until the final excavation of the 
beds of the rivers through the basement clay and marl to depths of 
about 30 and 50 feet respectively, as evidenced by the banks over- 
hanging the present rivers in various localities, had reduced them to 
their present levels. Finally, the rivers having attained a state of 
equilibrium, they deposited the silt and vegetable matter brought 
down in times of flood, and spread them out in beds of modern 
alluvium. The foregoing outline of the probable succession of 
events belonging to the later geological history of the district is, it 
must be confessed, manifestly imperfect, and inadequate to explain 
satisfactorily many of the facts, partly owing to the necessarily 
meagre amount of positive evidence attainable, and partly depend- 
