30 
THE LOWER LIAS OF KEYNSHAM. 
The north wall is formed of red Keuper marls, against which 
the Lias beds, seen in the west wall, rest, having been thrown 
down to the south. 
The Lias beds belong to the upper Angulatus and lower 
Arietes zones. Large ammonites, etc., can be obtained from 
the stack of stone near the entrance. 
Exposure 3. A quarry in work. 
A small fault, which strikes east and west across the 
middle of the quarry, separates Angulatus beds on the south 
from higher beds nearer the road. The downthrow is about 
fifteen feet to the north. 
The south portion of the quarry consists of the Angulatus 
series resting on the thick clay which forms a very conspi- 
cuous band at the base of the. section. In a trench, which is 
excavated all along at the base of the quarry wall, the hard 
beds beneath are well shown and large Limas are obtained 
very abundantly from these beds, as well as more sparingly 
from the beds just above the thick clay. Wald, perforata 
is also a very abundant fossil in these beds and occurs in 
the clay itself. 
The thick clay dies out at the south-east corner of the 
quarry, where it passes laterally into limestones. 
Only the lower portion of the Calcicosta series can be seen 
in this portion of the quarry. 
North of the fault there is a fine section, extending from 
the Calcicosta series at the base completely through the Arie- 
tes zone, up into the Oxynotus clay at the top. The following 
are the most interesting points to be made out : — 
The thick top block of the Calcicosta beds, crowded with 
Rh. calcicosta^ contains numerous bisulcate ammonites and 
a very few specimens of Bel. acutus. 
The Bisulcatus beds are extremely rich in large ammonites. 
The upper Semicostatus beds (characterized by Am. geo- 
metricus) contain a band of thin, argillaceous limestones in 
