OTSr THE DEVONIAN ROCKS OF SOUTH DEVO^^ 487 



29. TJie Devonian Rocks of South .Devon. By W. A. E. Ussher, 

 Esq., E.G.S., of the Geological Survey of England and Wales. 

 (Eead April 30, 1890.) 



By permission of the Director-General of the Geological Survey 

 of the United Kingdom. 



CONTKNTS. 



§ L Introduction. 

 § II. General Description. 

 § III. Eelations of the Culm ani» Devonian. 



§ IV, Lower Devonian. 



1. Torquay Area. 



2. Paignton Area. 



§ V. Middle Devonian. 



1. Eifeliau. 



2. Middle Devonian. 



3. Middle- and Upper-Devonian Limestones. 



§ VI. The Asiiprington Volcanic Series. 

 § VII. Uj'pek Devonian. 



1. Massive Limestones. 



2. Goniatite-beds. 



3. Cypridinen-Schiefer (Entouiis-slates). 



^5 VIIT. Conclusions. 



§ I. Introduction. 



'^' In South Devonshire the rocks are greatly disturbed, broken b}'- 

 faults, standing at various angles, folded, and distorted ; eruptive 

 rocks frequently cut through them, and beds of volcanic ash are 

 interstratified with them. Hence has arisen great dispute and 

 uncertainty as to the true order of succession of deposits, although 

 their fossils were referred to the Devonian age nearly fifty years 

 ago. It will be seen without comment that the South Devonshire 

 sections, from which most of the Middle- and Lower-Devonian fossils 

 have been obtained, are valueless for determining the order of 

 sequence of the faunas. There are many places (I saw such near 

 Newton-Abbot) where limestones, a]jpearing very similar in colour 

 and structure, and within a stoue's throw of each other, hold distinct 

 faunas. In fact, the interpretation of the order of the beds is a 

 matter of the greatest difHculty, even when occasional fossils appear.'' 

 Here is the geology of South Devon as epitomized by Professor 

 H. S. Williams, of Ithaca, N.Y., in a paper read before the American 

 Association for the Advancement of Science as lately as Aug. ^30, 

 1889. Explorations in the rocks of Devonshire gave rise to the 

 Devonian System; explorations in France, Belgium, Germany, Russia, 

 and North America have made us acquainted with the succession of 



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