XV.] CAMBRIAN AND SILURIAN IN EUROPE. 381 



Murchison included the Arenig rocks), " into which it gradu- 

 ates conformably." (Loc. cit., 4th ed. p. 46.) In each of these 

 cases, on the contrary, according to Eamsay, there is observed 

 " a break very nearly complete both in genera and species, and 

 probable unconformity " ; the evidence of the palseontological 

 break being furnished by the careful studies of Salter ; while 

 that of the stratigraphical break, as we have seen, leaves no 

 reason for doubt. (Mem. Geol. Sur., III. Part II. pages 2, 161, 

 234.) The student of Siluria soon learns that in all cases 

 where Murchison's pretensions were concerned, the book is 

 only calculated to mislead. 



The reader of this history will now be able to understand 

 why, notwithstanding the support given by Barrande, by the 

 geological survey of Great Britain, and by most American 

 geologists to the Silurian nomenclature of Murchison, it is 

 rejected, so far as the Lingula flags and the Tremadoc slates 

 are concerned, by Lyell, Phillips, Davidson, Harkness, and 

 Hicks in England, and by Linnarsson in Sweden. These 

 geologists have, however, admitted the name of Lower Silu- 

 rian for the Bala group or Upper Cambrian of Sedgwick ; a 

 concession which can hardly be defended, but which appar- 

 ently found its way into use at a time when the yet unravelled 

 perplexities of the Welsh rocks led Sedgwick himself to pro- 

 pose, for a time, the name of Cambro-Silurian for the Bala 

 group. This want of agreement among geologists as to the 

 nomenclature of the lower palaeozoic rocks, causes no little 

 confusion to the learner. We have seen that Henry Darwin 

 Rogers followed Sedgwick in giving the name of Cambrian to 

 the whole paleozoic series up to the base of the May Hill 

 sandstone ; and the same view is adopted by Woodward in his 

 Manual of the Mollusca. The student of this excellent book 

 will find that in the tables giving the geological range of the 

 mollusca, on pages 124, 125, and 127, the name of Cambrian 

 is used in Sedgwick's sense, as including all the fossiliferous 

 strata beneath the May Hill sandstone. On page 123 it is, 

 however, explained that Lower Silurian is a synonyme for Cam- 

 brian, and it is so used in the body of the work. 



