272 THE GEOLOGICAL STRTTCTITBE OF SOUTH COMiTWALL. 



invertebrate marine fauna, such, as corals and shells, are 

 entirely absent, and their place is taken by the remains of 

 numerous fishes, presenting quite a contrast to the typical 

 Devonian of England. In Cornwall, however, the Devonian 

 strata contain quite a co-mingling of the testacea of the rest of 

 England, and of the fishes of Scotland, serving as a link to unite 

 the Devonian and Old Eed Sandstone into one great life system, 

 a character which it also possesses as developed in Eussia. 



The object of this paper has not been to enter into any 

 lengthened detail on the geology of this portion of Cornwall, 

 but rather to remove what I consider to be errors which only 

 tend to complicate and confuse its study. 



The brief outline I have indicated of what I consider to be 

 the structure, age, and order of succession of the rocks forming 

 this portion of Cornwall, curiously enough is precisely the same 

 as obtains in Brittany, where the Upper Silurian is also absent. 

 Further, throughout the whole of the various members of these 

 formations as developed in that country, there is a most com- 

 plete conformity, such as we consider exists in Cornwall. 



That very much requires to be done for Cornish geology 

 will be most obvious to its best workers ; much requires yet to 

 be done in assigning large tracts of the strata to their proper 

 formations, in defining their horizons and boundaries, in 

 detailing the structures the rocks assume in forming the surface 

 of the covintry, in working out their life history by carefully 

 collecting and tabulating their fossil contents, and also in 

 studying the relations of the granite to the stratified rocks, and 

 the various igneous outbursts that have from time to time taken 

 place, noting those that are of contemporaneous origin and 

 those that are of subsequent date to the strata. 



Again the strata in various parts of the county under 

 consideration, present many points of difficulty and of a very 

 problematic nature. Such an area occurs in the neighbourhood 

 of Mevagissey, where the strata are very much disturbed, standing 

 quite vertical and forming what appears to be the axis of a 

 series of folds, which tends greatly to increase the difficulty in 

 tracing out the sequence of the strata in this rather complicated 

 district. 



