LOWER LIAS : MliXDIP HILLS. 97 
also faulted : for they include portions of division 5, because 
among the wreck of marly beds we find A. Turneri and A. 
stellaris? Still further to the west we find the famous Rhsetic 
section of Blue Anchor, with the basement-beds (1) of the Lower 
Lias on top. 
It is noteworthy that in this district, where the Rhastic Beds and 
Lower Lias border the older (Devonian) rocks, they do not 
exhibit the conglomeratic c >ndition3 shown in some other places. 
It seems probable that the beds are faulted against the Devonian 
Rocks, near Selworthy, where the dip of the Lower Lias, &c. ha3 
been noted as from 15 to 23, by Mr. J. H. Blake; at any rate 
we have no evidence pointing to a Liassic sea-margin anywhere 
in West Somerset. 
Mendip Hills. 
It has been shown that in some places, the lower beds of the 
Lower Lias border the Mendip Hills and fringe its slopes, and 
that on its summit there are patches of Lower Lias in places. 
There can be no doubt, therefore, that some portions of the 
Mendip area were above water, either as a promontory connected 
with the Glamorganshire area, or as islets in the Liassic seas. It 
is difficult to estimate the amount of sediment accumulated on its 
surface, for the Liassic beds, where preserved, are not of great 
thickness, and show as a rule only the lower zone of Ammonites 
planorbis. 
Near Frome, however, in Vallis, Nunney, and other ravine?, we 
find an exceeding variable series of deposits resting on the Car- 
boniferous Limestone and older rocks. In some places the 
Inferior Oolite rests directly on the Carboniferous Limestone ; in 
others we find intervening beds of Rhsetic age, Lower Lias and 
Middle Lias. 
The surface of the Carboniferous Limestone as pointed out by 
De la Beche,* and others, is in many places planed off in a 
remarkably even manner, so that horizontal beds of Dolomitic 
Conglomerate (Trias), Lias, and newer deposits, rest on an even 
surface of the highly inclined Carboniferous Limestone. The 
surface of these older strata is not uniformly level over extensive 
areas; it would appear rather that, in addition to occasional islets, 
or other inequalities, there were various platforms upon which 
divisions cf Lias and newer strata were accumulated in a more or 
less attenuated form. In some cases these deposits were removed 
before succeeding accumulations were laid down : so that the 
platform or terrace may have been formed at an earlier stage than 
that of the deposits now resting on it. The varying position-3 
occupied by these Secondary strata on the flanks and higher 
grounds of the Mendips, are likewise in part due to marginal de- 
posits being laid down at different relative levels, and in part to 
subsequent faulting or irregular elevation. 
* Mem. Geol. Survey, vol. i. pp. 269, 287, &c. 
E 70859. O 
