J 



SEEIES OF THE DEVON COAST-SECTION. 161 



more likely that this is to be found in the lower part of the sand- 

 stone-marl series of the Keuper (as here defined) ; and those who 

 are familiar with the succession in continuous sections of the Bunter, 

 Muschelkalk, and Keuper of the German area {e. g. in the hills about 

 Jena, in the Ramsberg and Horselberg on the north side of 

 Thiiringen, and in the valley of the Upper Neckar) will not, I think, 

 be prepared to deny that such a partial equivalency may exist. But 

 when all this is admitted, it is of high importance not to forget the 

 great attenuation of the Muschelkalk and its gradual assumption 

 of a more arenaceous character in the direction of the British 

 area *. 



It would not be right to overlook the fact that there is much less 

 clearness of definition (stratigraphically) between the Bunter and 

 Keuper of the Devon area than there is between the same two 

 formations in those parts of the Midlands (e. g. about JN'ottingham) 

 where the Upper Bunter is wholly, or for the most part, wanting. 

 When this is taken into account along with the fact of the unusually 

 calcareous nature of the 150 feet or so of strata above the Lower 

 Keuper sandstones, and with the further fact that many of the 

 limestones of the Muschelkalk contain more or less clay (Credner, 

 Elem. der Geol. p. 497), it does not seem unreasonable to recognize a 

 possible homotaxial equivalency between this group of beds and the 

 Muschelkalk. The suggestion of Mr. J. H. Blake, with reference to 

 another portion of this region which Mr. Ussher has quoted f, is 

 therefore probably deserving of more consideration than he seems 

 willing to allow. 



YI. I stated four years ago (Quart. Journ. Geol. Soc, August 

 1884), after my work in Central Germany, with reference to the 

 Dyas and Trias of Central Europe, that " not only is there a strati- 

 graphical break, but a marked petrological contrast between the two 

 groups" (p. 396); and, again, "The direct relation of the Ptothlie- 

 gendes to the character of the adjacent (older) land, which is so 

 marked throughout that formation, and is generally wanting in the 

 formations of the Trias, serves to establish a general broad physical 

 distinction between the two groups of strata, as they are developed 

 in Central Europe " (pp. 397, 398). 



These statements (^mutatis mutandis) I consider applicable to the 

 Devon Eed Rock Series. The great breccia-marl series consists of 

 the roughly assorted direct |)roducts of atmospheric waste and degra- 

 dation of the Devon palaeozoic land, the true Trias of the region 

 being derived partly from these older sediments, and partly com- 

 posed of materials brought into the basin from other areas, owing 

 to some of those changes in physiography of which the Post-Car- 

 boniferous rocks contain such plain records over great parts of the 

 European area. 



Some remarks of Mr. Ussher himself (Quart. Journ. Geol. Soc. 

 vol. xxxii. pp. 393, 394) show that the difficulties of grouping the 



-=«• Vide Geol. Mag. dec. ii. vol. ix. p. 276 ; also Quart. Journ. Geol. Soc. 

 August 1884, p. 401. 

 t Log. cit. p. 380. 



