PRELIMINARY REMARKS. 3 



of Ireland the Coomliola grits and Carboniferous slate pass downwards into Old Red 

 Sandstone, and upwards into Carboniferous Limestone ; and they arc considered by Mr. 

 Jukes either to be the lowest part of the Carboniferous series, or else to form a distinct 

 group together with the upper half of the Irish Old Red Sandstone, which is stratigraphi- 

 cally quite unconnected with the lower half. Further, it must be remembered that for 

 many years, in Devon and Cornwall, Silurian and Devonian rocks were all massed together 

 and called by one name. But we know that there must be an unconformity discoverable 

 between the Lower Silurian and Devonian rocks, if properly searched for; and analogy 

 would lead us to expect, from the strong breaks in organic succession, that the same 

 broken stratigraphical relations — lapses of unrepresented time — must exist between the 

 various members of the typical Devonian series, just as they certainly occur in what 

 geologists consider their equivalents, the Old Red Sandstones of Scotland and of Ireland." 1 

 Mr. Pengelly, whose knowledge of Devonshire and Cornwall Devonian Geology is very 

 considerable, informs me that, according to Professor Sedgwick's system, (' Quart. Journ. 

 Geol. Soc.,' vol. viii,) the slates and limestones of North Devon and Cornwall, as those 

 of LooCj Woolborough, Ramsleigh, Hope's Nose, Glampton Creek, Galmpton Point, Black 

 Hall, St. Veep, Polruan, and Whitesand Bay, belong to the lowest Devonian group found 

 in the two counties ; that he followed him in his paper on the distribution of the fossils of 



1 The late D. Sharpe, writes in June, 1852 (' Journ. Geol. Soc.,' vol. ix, p. 22), that he urged Mr. Morris, 

 in 1843, to separate from the Devonian system the fossiliferous beds of Pilton and Barnstaple (and, 

 perhaps, Marwood) in North Devon, and those of Tintagel and South Petherwin in the South, and to 

 place them in that group of strata which corresponds to the Lower Limestone-shales of Northumberland 

 and the Scotch coal-field. 



Mr. Salter thus classes the North Devon strata in descending order. 



I. Pilton Beds. — An alternating series of calcareous sandstones and grey shales, with their bands 

 cf limestone and grey slate, full of fossils, several hundred feet thick. 



II. Marwood Beds. — A thick series of greenish-grey grits, with bands of Cuculcea and Avicida in 

 abundance, with olive slate in which a Lingula occurs plentifully (both Mr. Salter and Sir 

 II. de la Beche make the Lingula-beds to be older than the Pilton group), they run parallel 

 with, and in close proximity to the Cuculsea-beds. 



III. Mokte Group. 



No Devonian Brachiopoda have been found in Scotland. The Dron Shales form a small patch in 

 Lower Strathearn, dipping southwards into the base of the Ochils and towards the coal-fields of Fife, but 

 separated by the entire breadth of the Orchils and the Old Red plains of S. Watheden. Mr. D. Page, 

 Professor Harkness, Mr. Salter, Mr. Powrie, Professor R. Jones, Mr. Etheridge, and myself, are inclined to 

 regard them a3 Lower Carboniferous, and not Devonian, as some have supposed. They contain but a 

 single species of Brachiopoda, which appears referable to Mhynchonella pleurodon : the other organisms, 

 although generally very imperfectly preserved, are of a Carboniferous type, Leperditia subrecta (Portlock's 

 Ci/pris suhrecta), a common Lower Carboniferous fossil, having been also recognised by Mr. Jones. 



The Devonian formation is largely represented in Ireland, and especially in the southern portion of 

 the island ; but, with the exception of a few localities wherein plants, fish-scales, and Anodon Jukesii have 

 been found, it is non-fossiliferous, and I have not heard of any Brachiopod having been hitherto met 

 with. 



