1870.] GUNN—FOREST-BED AND CHILLESFORD CLAY. 503 
From this brief description it is obvious that the term “ Forest- 
bed” is inadequate to express so varied a formation, which, judging 
by its changes of level and of its fauna, must have continued a very 
long time ; and I beg to suggest that the “ Forest-bed series” would 
be a better name. ‘The want of proper divisions has led to many 
complications, especially in the palzontological department. 
It might be supposed that it would be easy to ascertain the posi- 
tion of a bed of such duration and extent ; but such is far from being 
the case. It has a nearly uniform horizon on the level of the water, 
and every attempt to reach the bottom of it has been foiled by the 
water rising. 
It is evident that it must lie between the Chalk, or London clay, 
below and the Chillesford clay above. In the inland section the only 
two intervening beds are the supposed Mammaliferous crag of Mr. 
Charlesworth and the Marine crag, which may be seen to advantage 
at Bramerton and Thorpe. Between these two beds there does not 
appear to be any break for the intercalation of the Forest-bed 
series; for they are deposited in succession upon each other in 
increasingly deeper water. The Mammaliferous crag was supposed 
to contain the Mastodon arvernensis, and has therefore been re- 
garded as older than the Forest-bed, which has not been known to 
yield the Mastodon. Where, then, can the Forest-bed be placed in 
the inland section, either in point of time or of superposition ? 
I beg to suggest the following solution. All the specimens of 
Mastodon arvernensis, so far as I can ascertain, have been found, to- 
gether with Hlephas meridionalis and several species of Cervus, in a 
stony bed, one or two feet thick, between the surface of the chalk and 
the Fluvio-marine and Marine Crags ; and, consequently, those crags, 
with the exception of a few water-worn fragments and the teeth of 
Arvicole, are nearly non-mammaliferous. It seems probable, there- 
fore, that here may be a break for the intercalation of the Forest-bed, 
and that the Fluvio-marine and Marine Crags ought to be detached 
from this stony bed, with which they have hitherto been incorporated 
under the name of Mammaliferous crag. The stones appear to be 
derived from the disintegrated chalk, which is worn down both by 
the chemical and mechanical action of water. 
Reference to the accompanying diagram (p.554) may makethis more 
intelligible. The chalk presents an inclined plane, upon which the 
beds from the London clay upwards have been deposited in succes- 
sion. It is evident, therefore, that the chalk (or portions of ity 
was subaérial until covered by each successive deposit, viz.— 
From a, after the Antwerp crag. 
aes, >»  Forest-bed. 
shan Cs: ,» Freshwater bed. 
apr i »,  Fluvio-marine. 
ane, ». Marine. 
Thus there was left a land surface upon the chalk from time to time, 
on which the mammals of successive periods may have lived. Con- 
sequently Mastodon arvernensis might have lived and died upon that 
VOL, XXVI.—PART I. 2k 
