No. 3.] HUNT — ON CAMBRIAN AND SILURIAN. 307 



rocks in this latter (their typical region), it was because he saw 

 them passing into the overlying Bala beds. There was, in the 

 error by which he placed below the Llandeilo, strata which were 

 really above them, no ground whatever for afterwards including 

 in his Silurian system, as a downward continuation of the Llan- 

 deilo rocks (which are the basal portion of the Bala group), 

 the whole Festiniog group of Sedgwick; whose infra-position to 

 the Bala had been shown by the latter long before it was known 

 to be fossiliferous. 



It was however claimed by Murchison that no line of separa- 

 tion can be drawn between these two groups. The results of 

 Ramsay and of Salter, as set forth in the address of the former 

 before the Geological Society in 1863, and more fully in the 

 Memoirs of the Geological Survey [vol. III. part 2] published 

 in 1866, with a preface by himself, as the director of the Survey, 

 are completely ignored by Murchison. The reader familiar with 

 these results, of which we have given a summary, finds with sur- 

 prise that in the last edition of Sihn-ia, that of 1867, they are 

 noticed in part, but only to be repudiated. In the five pages of 

 text which are there given to this great Middle C-nnbrian divi- 

 sion, we are told that the distinction between the Lower Trema- 

 doc and the Linouhi-fl isrs '' is difficult to be drawn," and that the 

 Upper Tremadoc slate passes into and forms the lower part of 

 the Llandeilo, " into which it graduates conform. .bly." (Siluria, 

 4th ed. p. 46.) In each of these cases, on the contrary, according 

 to RaraSiiy, there is observed " a break very nearly complete both 

 in gener.i and species, and prob .ble unconformity;" the evidence 

 of the p ileontologic .1 break being fuinished by the careful studie8 

 of Salter; while that of the stratigraphic.d break, as we have seen, 

 leaves no reason for doubt. [Mem. Geol. Sur. Ill, part 2, p; ges 

 2, 161, 234.] The student of Slhiria soon learns that in all cases 

 where Murchison's pretensions were concerned, the book is only 

 calculated to mL-iJead, 



The reader of this history will now be able to understind why, 

 botwithstanding the support given by B arrande, by the Geologi- 

 cal Survey of Great Britain, and by most American geologists to 

 the Silurian nomenclature of Murchison, it is rejected, so f >r as 

 the Lingula-fligs and the Tremadoc si ites are concerned, by 

 Lyell) Phillips, Dividson, Harknesa and Hicks in England, and 

 by Linnarsson in Sweden. These authorities have, however, 

 admitted the name of Lower Silurian for the Bala group or 



