BRITISH AVONIAN CONODONT FAUNAS 259 
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Abundance factor= Lotal_ no. of specimens Total weight of sample 
Total weight of sample in kilograms 
Fic. 72. Lithological section of the Dez Subzone of the North Crop of the South Wales 
Coalfield showing the abundance factor of conodonts in each sample, and the total weight 
of limestone dissolved. For details of collecting localities see Fig. 7 and also p. 33. 
