198 A. Chamjjernowne — The Devonians of N. and S. Devon. 



Silurian and the Coal Measures are, as a whole, singularly remark- 

 able for not doing. 



An invaluable heritage left us by William Smith is the idea of 

 " strata identified by organic remains " ; but yet there remain the 

 questions of currents, habitat and sea depth, life provinces, and so 

 forth : and it may be that the •' Devonian " or " Eifelian " life 

 province of the Lower Carboniferous epoch is one of the most 

 remarkable and well-defined life provinces of the past. But here 

 we touch a whole circle of thought, to enter which would be beyond 

 the scope of the present sketch. 



The work must still be one of time, and I agree with the 

 substance of Prof. Warington Smyth's remarks at Plymouth, that 

 but little exhaustive work can be done before the Six-inch Maps 

 are in the hands of the Geological Surveyors. 



Should they show the Jukesites to be wrong, and succeed in 

 proving that the String ocephahis, as compared with the Productus, 

 limestone, is something not " sui generis " merely, but sui cBvi also, 

 no one will less regret it, save for his admiration for the master 

 mind of Jukes, than the writer of this paper. 



Additional Note. — In speaking of the Stringocephalus Limestone as 

 of Lower Carboniferous age, it is fair that I should guard myself 

 from possible misapprehension. 



Where two limestones run parallel for some distance, separated 

 from each other by mechanical rocks, and characterized each by its 

 own fossils, clearly we cannot give the same name to both, although 

 we may include both in the same great system. 



To explain more clearly. Suppose we are tracing a band of 

 Posidonomya limestone among Culm Shales from west to east of 

 North Devon, we find that, about Westleigh and Holcomb Eogus, 

 changing its character, it approaches that of the Carboniferous 

 Limestone of the Mendips. Still, as Mr. Horace Woodward has 

 observed, it may represent only a part of that formation. Also, we 

 know from Murchison's and Sedgwick's writings that if we follow 

 the Posidonomya beds along the Westphalian frontier towards the 

 Rhine, at Cromford near Eatingen they put on the characters of 

 true Carboniferous Limestone with well-known Producti. This 

 iipper group is accompanied at som-e depth below by another lime- 

 stone, the gi-eat Westphalian limestone, the Eifler kalk. 



The strata by which the two limestones are separated are those 

 known as Flinz (lowest), Kramenzel-stein, and (Spirifer-) Ver- 

 neuili Schiefer, the whole classed as "Upper Devonian." Murchison 

 (Siluria, 4th ed., p. 397) stated that, where most expanded, the 

 group has a thickness of 1300 feet (1000 for the "Flinz" at 

 Nuttlar). 



Now, what parallel is there between this 1300 feet maximum, 

 with no Old Red Sandstone, and the vast pile of sedimentary rocks 

 represented by the distance from Ilfracombe to the Culm limestone 

 at Fremington more than 9 miles as the crow flies? A pile, of which 

 a part only, "the Pickwell Down sandstones," have been estimated at 

 3000 feet, and parts of the series north and south of them at higher 

 figures stQl ! 



