XV.] CAMBRIAN AND SILURIAN IN EUROPE. 379 



Sedgwick. But when, still later, a further " appeal to nature " 

 led to the discovery of " characteristic new forms," and estab- 

 lished the existence of a " type of fossils in the mass of the 

 Cambrian rocks, different from those of the Lower Silurian 

 series," Murchison was bound by his own principles to recog- 

 nize the name of Cambrian for the great Festiniog group, with 

 its primordial fauna, even though Barrande and the govern- 

 ment surveyors should unite in calling it Primordial Silurian. 



He, however, chose the opposite course, and now attempted 

 to claim for the Silurian system the whole of the Middle 

 Cambrian or Festiniog group of Sedgwick, including the Tre- 

 madoc slates and the Lingula flags. The grounds of this 

 assumption, as set forth in the successive editions of Siluria 

 from 1854 to 1867, and in various memoirs, may be included 

 under three heads : first, that the Lingula flags have been found 

 to exist in some parts of his original Silurian region ; second, 

 that no clearly defined base had been assigned by him to his 

 so-called system ; and, third, that there are no means of draw- 

 ing a line of demarcation between those Middle Cambrian 

 formations and the overlying Llandeilo. 



With regard to the first of these reasons, it is to be said 

 that the only known representatives of the Lingula flags in 

 the region described by Murchison in his Silurian system are 

 the black slates of Malvern and some scanty outliers which, 

 in Shropshire, lie between the old Longmynd rocks and the 

 base of the Stiper-stones. The former were then (as has already 

 been shown) supposed by him to belong to the Llandeilo, or 

 rather to the passage-beds between the Llandeilo and the Cam- 

 brian (Bala) ; while with regard to the latter, Eamsay expressly 

 tells us that they were not originally classed with the Silurian, 

 but have since been included in it. (Mem. Geol. Sur., III. 

 Part II. page 9 ; and 242, foot-note.) 



The Llandeilo beds were by Murchison distinctly stated to 

 be the base of the Silurian system (Silurian System, 222) ; 

 and it was further declared by him that in Shropshire (unlike 

 Caermarthenshire) " there is no passage from the Cambrian to 

 the Silurian strata," but a hiatus, marked by disturbances 



