254 C. SCHUCHERT — LOWEK HELDERBERG— ORISKANY FORMATIONS 



equivalents. As a name, therefore, Old Red sandstone has priority over 

 that of Devonian, but since in the latter area marine fossils occur, en- 

 abling similar horizons to be identified elsewhere, this systemic name 

 lias supplanted that of the Old Red sandstone, and is now generally 

 recognized the world over. In regard to the latter formation, Geikie* 

 writes as follows : 



" In Wales and the adjoining counties of England, where the typical develop- 

 ment of the Silurian system was worked out by Murchison, the abundant Silurian 

 marine fauna disappears in the red rocks that overlie the Ludlow group. From 

 that horizon upwards in the geological series, we have to pass through some 10,000 

 feel or more of barren red sandstones and marls, until we again encounter a copious 

 marine fauna in the Carboniferous limestone. It is evident that between the dis- 

 appearance of the Silurian and the arrival of the Carboniferous fauna, very great 

 geographical changes occurred over the site of Wales and the west of England. For 

 a prolonged period, the sea must have been excluded, or at least must have been 

 rendered unfit for the existence and development of marine life, over the area in 

 question. The striking contrast in general facies between the organisms in the 

 Silurian and those in the Carboniferous system, proves how long the interval be- 

 tween them must have been. 



"At present the general belief among geologists is that, while in the west and 

 north of Europe the Silurian sea-bed was upraised into land in such a way as to 

 inclose large inland basins, in the center and southwest the geographical changes 

 did not suffice to exclude the sea, which continued to cover that region more or 

 less completely. In the isolated basins of the west and north, a peculiar type of 

 deposits, termed the Old lied Sandstone, is believed to have accumulated, while in 

 the shallow seas to the south and east, a series of marine sediments and limestones 

 was formed, to which the name of Devonian has been given. It is thus supposed 

 that the Old Red Sandstone and Devonian rocks represent different geographical 

 areas, with different phases of sedimentation and of life, during the long lapse of 

 time between the Silurian and Carboniferous periods. . . . 



" That the Old lied Sandstone of Britain does represent the prolonged interval 

 between Silurian and Carboniferous time can be demonstrated by innumerable sec- 

 tions, where the lowest strata of the system are found graduating downward into 

 the top of the Ludlow group, and where its highest beds are seen to pass up into 

 the base of the Carboniferous system. . . . It is quite possible, therefore, that 

 the lower portions of what has been termed the Devonian series may, in certain 

 regions, to some extent represent what are elsewhere recognized as undoubtedly 

 Ludlow or even perhaps Wcnlock rocks. f 



" Yet even at the best the Devonian rocks of this classical region, though they 

 served as the type formations of the same geological age elsewhere, are much less 

 clearly and fully developed than those of the Rhine country and other parts of 

 the continent. It is rather from the sections and fossil collections of central 

 Europe than from those of England that the stratigraphy and paleontology of the 

 Devonian system are to be determined." 



* Text-book of Geology, :;<! ed., L893, pp. 777-77.\ 7s:;. 

 See an/, , Peach and Home. 



