A HISTORY OF CORNWALL 



The ' killas ' which separates the conglomerate of the Meneage 

 district from the fossiliferous Devonian strata of the Newquay district, 

 has been divided into three lithological divisions, viz. the Portscatho 

 series, the Falmouth series and the Mylor series. 1 All these divisions are 

 composed of argillaceous and sandy alternations, and all are characterized 

 by the absence of limestone. Their lithological types are however suffi- 

 ciently distinct to admit of their being separable on geological maps. 

 The Portscatho and Mylor series are blue and dark in colour ; the Port- 

 scatho contains the coarser sandstone beds, while the Mylor rocks besides 

 being more shaly are more distinctly banded. The Falmouth series exhibits 

 greater variation, is usually buff in colour, but includes zones which are 

 purple and red. The rocks also appear to be of lesser thickness than either 

 of the two series which they divide. Their occurrence in the Fal basin 

 between Falmouth and Truro in a series of parallel lenticles is an ad- 

 mirable illustration of the geological structure of the county ; for although 

 the strata have a general south-easterly dip, and we are apparently cross- 

 ing the strike from the coast to the heart of the county, yet instead of 

 getting deeper in the stratigraphical series we are on precisely the same 

 geological horizon at Truro as at Falmouth, the intervening ground being 

 made up of a succession of isoclinal folds. 



On leaving the barren belt occupied by these rocks we find between 

 Holywell Bay and Boscastle on the north coast, and between St. Austell 

 Bay and the Tamar on the south coast, an assemblage of strata which 

 is not only fossiliferous, but in which limestones occur. The fossil re- 

 mains with which they are charged leave little doubt that this belt is 

 occupied in the main by Devonian strata, but until the region has 

 been more closely investigated it would be unsafe to assume that an area 

 so folded is entirely restricted to that formation. It is possible that the 

 fine grained conglomerate of Probus and Grampound and the Nare Point 

 conglomerate may represent an unconformity dividing the Silurian and 

 Devonian formations. 



As the northern coast of Cornwall truncates the Culm Measures as 

 well as Devonian rocks, while the former are not seen on the south 

 coast, a brief description of the fossiliferous rocks of north Cornwall 

 will sufficiently indicate our knowledge of the palasontological remains 

 that are entombed within the strata. 



For the following description of those formations we are indebted 

 to Mr. Howard Fox : 



The rocks of the north coast of Cornwall do not yield fossils in as 

 good a state of preservation as those of the south-east coast and of the 

 South Petherwin beds near Launceston. Between Holywell Bay and 

 Newquay no determinable fossil of interest has as yet been found. At 

 Newquay Mr. Clement Reid has recently collected a considerable num- 



1 J. B. Hill, Summary of Progress of the Geological Survey for 1898, p. 97. 



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