244 BRITISH AVONIAN CONODONT FAUNAS 
(b) Previous research 
A critical review of previous research on Carboniferous conodont faunas is given, 
together with a review of the present status of Carboniferous stratigraphical correla- 
tion (p. 17). 
(c) Collecting localities 
Samples have been collected from each of five major depositional areas. This has 
provided an indication of the degree of variability of conodont faunas both within 
and between depositional basins. In all some 3% tons of limestone has been 
processed. 
Avon Gorge, Bristol 
Detailed sampling of this area has involved the digestion of some 189 ‘ major’ 
rock samples, most of them about ro lbs in weight. Every ro ft. of the section 
was sampled, and these samples were supplemented in critical parts of the succession 
by others taken at 5 ft. and 2 ft. intervals. The stratigraphy of the collecting areas 
is described in detail (p. 18). 
North Crop of the South Wales Coalfield 
A series of eleven localities in Brecknockshire and Monmouthshire was used to 
construct a composite Lower Carboniferous section, and small collections were made 
from Gower and Pembrokeshire. The middle part of the Avonian succession is 
generally not fossiliferous in this area, but the higher parts of the Dibunophyllum 
Zone have been used to complement the zonal scheme for the lower part of the 
section, established in the Avon Gorge. 
Shropshire 
The thin development of the Z and K Zones at Farlow and Oreton have yielded 
well-preserved faunas (p. 25). 
Yorkshire 
Sampling of the Yoredale succession in the type area has provided material for a 
reconnaissance survey of Yoredale conodont faunas. They show close similarities to 
those of the higher zones from the South Western Province. 
Scotland 
Extensive collections have been made from Dunbar, Roxburgh, Midlothian, Fife, 
Ayrshire and Argyll. All the major limestones in the succession were sampled, some 
at intervals of six inches, and most yielded well-preserved faunas. 
(d) Methods of study 
Most of the 25,000 specimens which form the basis of the study were extracted by 
digestion of limestone in 8 % acetic acid. Methods of preparation and photography 
are described. The abundance of conodonts in each sample has been recorded 
(Figs 59-92). 
