76 
THE AVONIAN OP THE AVON GOROE 
In 1885,1 Prof. C. Lloyd Morgan, LL.D., F.E.S., F.G.S., 
published an extremely suggestive account of the Avon Gorge 
in which he pointed out the broad principles which have governed 
the formation of the Gorge itself and of its tributary depressions. 
The magnitude of the Great Fault and its extension on the 
Leigh Woods side of the river are also discussed in the same 
paper. The present communication will, it is hoped, serve as a 
necessary complement to the work of Prof. Lloyd Morgan by 
filling in detail, where he has already firmly sketched the broad 
outline. 
Mr. E. B. Wethered, F.G.S.,^ has dealt with the micro- 
structure of the rocks which form the Avon Sequence and has 
classified the local development of the Lower Carboniferous 
Rocks into broad lithological divisions. 
From 1902 to 1905, 1 was engaged upon the detailed examina- 
tions of the Carboniferous Limestone sequence in the Bristol 
Area, with the special object of determining the faunal sequence 
and of setting out a series of life- zones. The results of this 
investigation are described in my paper, ‘ The Palaeontological 
Sequence in the Carboniferous Limestone of the Bristol Area,’ 
to which reference has already been made. In this paper, the 
Avon Section is described in considerable detail and is adopted 
as the type-section for the Avonian of the South-Western Pro- 
vince. 
Fossil The following definitions explain the precise meaning 
Notation which is to be attached to the conventional symbols 
employed in the designation of fossils throughout this paper. 
A species is a form so completely described that the 
characters of two individuals, both of which are correctly referred 
to the same species, can only differ in degree of expression ; 
furthermore, all the individuals which constitute a species must 
^ ‘ Subaerial Denudation and the Avon Gorge.’ Proc. Bristol Nat. Soc. 
n.s. vol. iv. p. 171. 
2 ‘ On Insoluble Residues obtained from the Carboniferous Limestone 
Series at Clifton.’ Quart. Journ. Geol. Soc. vol. xliv. (1888), p. 186, 
