12 STRATA EXPOSED IN CONSTRUCTING FILTON-AVONMOUTH RAILWAY. 
f Marl, in nodules, brown withl 
^ I greenish grey centre / 
p Marls, greenish grey ... ... 9 6 
pd 1 Marls, red, to base of section as) on 
^ I now seen / 
The Lias is seen only in the cutting East of the tunnel. One 
specimen of Am. ( Caloceras) Johnstoni was observed among the debris, 
but the Ammonite could not be found in sitit, in fact the beds scarcely 
reach the level at which Ammonites would be expected. 
The White Lias is here rather thicker, but, in other respects the 
Lias agrees practically with the Ostrea and Pleuromya beds of the 
Filton cutting. 
The Gotham marble and upper portion of the Rhsetic are also 
seen only in the East cutting. 
At the West face of the tunnel the highest beds consist of the 
basal part of the Upper Rha^tic, and at this place the Naiadita bed 
(12) differs somewhat from its equivalent East of the tunnel. The 
sequence is as follows : — 
Upper Rh^tic at the West face of Charlton Tunnel. 
Feet. Ins. 
8 Limestone, yellowish grey ... ... ... 0 2 
9 Marl, with thin limestone ... ... ... 1 0 
10 Marl, hard, grey ; one specimen of Pecten valoniensis 0 3 
11 Shale, marly, yellowish grey, with thin limestone bands 1 0 
'(a) Limestone, bluish grey, gritty ... 1 in. 
(bj Limestone, yellowish grey, fissile, with 
some gritty courses ( Naiadita 
bed) cemented to ... ... 7 ins. 
(c) Limestone, bluish grey ... ... 2 ins. 
^(d) Marl, brownish grey ... ... 3 ins.^ 
The fossils of bed 12 are — Pecte^i valoniensis., Protocardiiun 
Phillipia^ium., Cardiitm cloacinum., Estheria mmuta var. Brodieana 
Darwinnla sp., Naiadita lanceolata, fish scales, teeth, coprolites, 
and occasionally bones. 
Naiadita and Darvoinula are common in 12 {h)) Estheria on the 
other hand is rare here, but common in 12 East of the tunnel. 
The fossils of the upper part of the Lower Rhsetic are much 
better preserved in the eastern than in the western cutting, due 
probably to their greater protection from surface conditions; below 
bed 16 there are no differences in this respect. 
There are three Pecten beds at Charlton, numbered 14, 16, and 
18 respectively. Bed 14 is irregular in occurrence and in character, 
but 16 and 18 are continuous and conspicuous beds, and these are 
referred to in this paper as the upper and lower Pecten beds. The 
commonest fossils in these beds are members of the genus Schizodns 
( = Pullastra Auctt.^, but since this genus ranges throughout the Lower 
Rhaetic, and specific determination of its members is not easy, it has 
little value as an index form. On the other hand Pecten valoniensis 
is easily recognised even when fragmentary, and its range is suffici- 
ently restricted and well defined to render it useful for index purposes. 
