34 
THE LOWER LIAS OP KEYNSHAM. 
The upper surface of these beds, which forms a platform in 
the quarry, is remarkable for the number of large specimens 
of Am. comjbeari ^hioh lie embedded in it. The upper beds 
belong to the Bisulcatus zone and consist of a thick series 
of limestones with very subsidiary clay partings. 
Exposure 8. A quarry. 
This exposure shows the massive Bisulcatus limestones 
below, capped by a thick shale which separates them from 
the prominent hard band formed by the Am. ohliquecostatus 
bed. This band contains abundant specimens of Am. 
obliquecostatus and also many phosphatic nodules. These 
nodules are of considerable interest, since they clearly mark 
the northern extension of the well known Phosphatic bed of 
the Padstock district. 
The upper Semicostatus beds consist of shales and thin 
impure limestones, very similar in all respects to the beds on 
the same horizon shown in exposure 3 north of Keynsham. 
The top of the section is formed of a thick clay, with a 
few beds of limestone nodules, from which a fragment of an 
Oxynoticeras was derived. 
The vertical section was constructed from data supplied by 
this exposure. 
III. Exposures on the Keynsham., Burnet, Marksbury 
Road (numbered 9, 10, 11). 
Exposure 9. A low, roadside section. 
At the base, the upper portion of the 0. irregularis beds, 
followed by a complete Calcicosta series a little thinner, but 
otherwise very similar to the same beds further north. We 
may notice, however, that Lima giyantea and its mutation, 
L. punctata, occur here as high up as the top block of the 
Calcicosta series. 
The Bisulcatus beds are much thinner than in the last 
group of exposures. They contain the usual large bisulcate 
ammonites as well as nautili, especially towards the top. 
