ETHEEIDGE DEVONIAN ROCKS AND FOSSILS. 683 



accumulated probably under freshwater conditions, within the gene- 

 ral area I have previously noticed, such being due to a series of 

 geographical changes dependent on the relative position of masses of 

 land and water, thus producing stratigraphical unconformity, and 

 partial zoological breaks ; yet, nevertheless, sufficient life-evidence 

 is left to enable us, through the Pish, Silurian genera of Trilobites, 

 and Brachiopoda, to link on and establish continuity, if not close 

 affinity, or even contemporaneity, and also to lead us to the con- 

 clusion that the Devonian series as a grouj) were deposited in a 

 different geographical area, and that the physical and palaeonto- 

 logical conditions were much the same here as over the region occu- 

 pied by them in France, Belgium and Prussia, through the whole 

 period of its accumulation ; added to which the ichthyic evidence in 

 the Lower, Middle, and Upper Devonian beds in the continental areas 

 is marked and decided. 



Professor Jukes states, p. 368, that " hy the hypothesis I now joro- 

 pose, the place of these marine Devonian heels will he fixed stratigra- 

 phically between the top of the Old Red Sandstone and the base of 

 the Coal-measures, in North Devon as in Ireland." Prom this 

 assumption, or proposition, and the way in which it is put, I entirely 

 dissent on eight grounds. 



1st. Because it is assumed that all the known Devonian species 

 of North Devon occur south of, or above, the Upper Old Red Sand- 

 stone of Pickwell Down, his Old Red Sandstone ; whereas 60 known 

 Devonian species, and thousands of feet of strata in regular sequence 

 are heloiv this line. 



2ndly. By this view we are led to believe that no older or lower 

 beds whatever, containing fossils, exist to the north of the line 

 assumed ; we are, however, enabled to divide the whole group below 

 into a Lower and a Middle series, the latter of which rests upon a set 

 of red sandstones and grits as marked, definite, and important as 

 those that overlie the Pickwell Sandstones, these are the Hangman 

 grits. 



3rdly. That the Lower or Lynton slates (Lower Devonian) nearly 

 1500 feet thick, and themselves divisible into three series, in their 

 turn rest upon the arched red sandstones of the Lynn valley and the 

 Poreland rocks. 



4thly. This hypothesis only accounts for the already well-known 

 position and group of the Upper Devonian series, which here in 

 North Devon (south of PickweU Down) overlie, as they do in the 

 south of Ireland, a series of red, green, and yellow sandstones &c. 

 (the Upper Old Red Sandstones), all that are there known. 



5thly. It is assumed that an extensive fault, or concealed anti- 

 clinal (before noticed), traverses the country from west to east, some- 

 where along the latitude of Pickwell Down, thereby causing the beds 

 properly called Upper Devonian to be repeated to the north, which 

 are therefore stated to be the same beds as those south of Morte Bay, 

 thus attempting to make the Lower or Lynton, and Middle or Ilfra- 

 combe series of the same age and to hold the same stratigraphical 

 position as the Upper Devonian at Baggy &c. 



