ETHERILGE DEVONIAN ROCKS AND FOSSILS. 679 



In the present case the intermediate position of the Devonian 

 series is assumed, although the Silurian is not seen or known in this 

 area ; but the upward succession into the Carboniferous is clear and 

 conclusive ; and upon this belief I base my premises as to the value 

 of the species contained in the underlying conformable rocks called 

 Devonian. 



There are 383 species of fossils known to occur in these rocks in 

 North and South Devon, which have no known or determinable stra- 

 tigraphical base. The rocks they do repose upon are prolally Silu- 

 rian ; whether Upper or Lower we know not, or whether conformable 

 or not we cannot say. 



The known British Silurian fauna consists of 1154 species*, only 

 one of which {Atrypa reticularis), I believe, is common to the 

 Devonian and the Silurian rocks. The seven species of fish that 

 occur in the passage-beds, and on the confines of the Upper Silu- 

 rian and the Lower Old Eed Sandstone, in the typical Silurian 

 area in Hereford and Worcestershire &c. have no value whatever 

 here, and therefore cannot be compared ; when it is absolutely 

 proved by stratigraphical demonstration that the lowest Devonian is 

 truly and identically equivalent to the Lower Old Eed Sandstone, we 

 may then say that there are 8 species known to be common to the 

 Devonian and Silurian formations. 



There are no marine forms in the Old Eed Sandstone ; but there are 

 383 in the Devonian rocks of the British Islands. 



Now it is well known that many thousands of feet of strata con- 

 sisting of red, grey, brown, and greenish slates, grits, and sandstones 

 occupy a large tract of country in North Devon, from Lynton to 

 Barnstaple, these marine fossiliferous beds overlying, in part at 

 least, what we have hitherto believed to be the lowest Old Eed Sand- 

 stone, the equivalents of the Lower Old Eed of the Silurian frontier, 

 which is totally void of fossils. 



The 383 new forms or species, then (for one only seems to have 

 migrated from a Silurian region), we must locate somewhere in time 

 as well as space. In the absence of any physical evidence to show 

 that the strata named " Devonian" in North Devon and elsewhere are 

 or are not contemporaneous with the Old Eed Sandstone, their stra- 

 tigraphical position is assumed, aided by palaeontological evidence, 

 and from the circumstance that only 56 species out of the 383 

 are known in the Carboniferous rocks which overlie the beds con- 

 taining them in North Devon (Tab. X.). Had the Carboniferous 

 rocks, however, stratigraphieally preceded this group, ^we shoidd 

 have placed them below the Devonian, and have referred the now 

 Devonian species to the Carboniferous as types. We are also now 

 better able to correlate, and to establish more direct contemporaneity 

 between, the Devonian and the Old Eed Sandstone, through Pish -re- 

 mains found in the known Devonian strata both in England and 

 Belgium, — Phyllolepis concentricus and Onclius having been found in 

 the Lower Devonian slates of Looe and Meadsfoot, Pteraspis in the 

 lowest Coblentzian rocks of Devon and AYassenbach on the Laa- 

 * r?V?« Table I. p. 615. 



