32 II. S. Williams — Devonian System of Devonshire. 



are regarded as having a general dip a little west of south, and 

 the outcrops lie in belts obliquely across the county from north- 

 west to southeast and are in order, from below upward, the 

 Lynton, Hangman, Combe Martin, Haggington, Ilfracombe, 

 Mortehoe, Pickwell Down, Baggy, Croyde, Pilton and Barn- 

 staple beds. The last are conformably overlaid by shales and 

 limestones and grits of the Carboniferous age which occupy 

 the interval separating them from the Devonian of South 

 Devonshire. Some faults are recognized but they are few 

 and simple. 



In South Devonshire the rocks are greatly disturbed, broken 

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

 eruptive rocks frequently cut through them and beds of vol- 

 canic ash are interstratified with them. Hence has arisen 

 great dispute and uncertainty as to the true order of succession 

 of the deposits although their fossils were referred to the De- 

 vonian age nearly tifty years ago. 



The most conspicuous member of the Southern Devonian is 

 the great Devon limestone. This is seen at Torquay, at New- 

 ton Abbot and farther south at Plymouth. It is blue or white 

 in color, and sometimes red and shaly near its base. There are 

 also great masses of argillaceous red shales which are consid- 

 ered as belonging above it. The character of the succession is 

 generally interpreted to be a series of red slates and shales and 

 grits followed by the limestone, which is again followed by a 

 red shale. At Torquay the shore for a mile south of the town 

 is made up of Triassic conglomerate with pebbles of Devonian 

 limestone, fine red argillaceous slates, not only laminated but 

 so twisted and contorted that neither lamination nor original 

 bedding can be followed continuously for more than a few 

 feet. With this are associated other red slates and limestones 

 and dikes of eruptive rock. These are all so confused that 

 except for the fossils found in them their order of sequence 

 could hardly be determined. 



One peculiar feature of the sections as seen about Ogwell 

 and Newton Abbott is the presence of beds regularly inter- 

 stratified with the limestones and shales, composed of volcanic 

 ash. These " Schalsteins," Mr. Ussher tells me, sometimes 

 contain fossils, and in places they are ten or twenty feet thick. 



It will be seen, without comment, that the South Devon- 

 shire sections, from which most of the middle and lower 

 Devonian fossils have been obtained, are valueless for deter- 

 mining the order of sequence of the faunas. There are many 

 places (I saw such near Newton Abbott) where limestones, 

 appearing very similar in color and structure, and within a 

 stone's throw of each other, hold distinct faunas. In fact the 

 interpretation of the order of the beds is a matter of the great- 

 est difficulty even when occasional fossils appear. 



