C. Lapworth — Classification of the Lower Palaeozoic Rocks. 9 



with that of the RocTcs of the First or Primordial Fauna of Barrande, 

 and is certain to be ultimately accepted everywhere among geologists, 

 from its naturalness, geologic distinctness and convenience of appli- 

 cation, not only in Britain and Western Europe generally, but also 

 among the ancient rocks of the continent of America. 



In the same way the general restriction of the title Silurian to the 

 strata that are comprehended between the line marking the base of 

 the Lower Llandovery, and that denoting the commencement of the 

 brackish or fresh-water conditions of the typical Old Red Sandstone, 

 appears equally inevitable. It covers the whole of the rocks of 

 Barrande's Third Fauna, which, as we have seen, must be erected into 

 a separate system as a matter of geologic convenience. It is 

 fortunate that the application of Murchison's title to them has never 

 been disputed, even by his bitterest opponent. 



The various titles at present in use for the intermediate system are 

 all certain to be discarded by the geologist of the future. They are 

 all more or less erroneous, ambiguous, or inconvenient. The re- 

 tention of the designation Lower Silurian would be as systematically 

 erroneous as it is historically unjust. To call it Upper Cambrian 

 would be to allow the followers of Sedgwick to commit the very 

 error they so emphatically condemn in the procedure of their oppo- 

 nents. The perpetuation of the Sedgwick- Murchison controversy, 

 by the general adoption of such a title as the Cambro- Silurian or 

 Siluro- Cambrian — even were it possible — would be, to say the least 

 of it, excessively unwise. Neither party is likely to forego its 

 claims when the object of contention is so conspicuously labelled 

 with the names of both. 



Before, however, we can take a single step to free ourselves from 

 the present difficulty, we must dispose of two formidable objections, 

 which, under the guise of universally accepted scientific principles, 

 have grown grey in the service of prolonging this unfortunate con- 

 troversy, and have, as yet, stubbornly barred the way to anything 

 like a peaceful solution. 



By those who still retain the Silurian System of the later days of 

 Murchison in all its magnitude, the argument of their founder that there 

 is no universal stratigraphical break to be detected among the Lower 

 Palaeozoics, at least as far down as the base of the Lingula Flags, is 

 held to be an overwhelming reply to all objectors. Similarly, it has 

 been the habit for their opponents, in their turn, to point triumphantly 

 to the local breaks in Britain between the Mayhill and Bala beds, as 

 affording in themselves a positive demonstration of the truth of their 

 own view that these formations belong to wholly distinct systems. 

 For a corresponding reason, also, the latter party claims for the 

 Cambrian all the fossiliferous strata that underlie the Llandovery, 

 from the fact that the physical succession among them is uninterrupted 

 by a general physical break. Of such pre-eminent value is this 

 principle considered, even by those who profess to stand aloof from 

 this controversy, that a strong tendency is abroad to sacrifice in 

 its favour the Old Bed Sandstone itself. 



To the field-geologist, pure and simple, who desires, above all 



