C. Lapioorth — Classification of the Lower Palceozoic Rocks. 5 



The points around which the strife is at its keenest bear upon the 

 question as to whether these three divisions are of equal classificatory 

 value, and if so, which party has the best right to give them their 

 names. 



The strict Murchisonian of the present day claims for the Silurian 

 all the fossiliferous strata that lie between the Archean and the 

 Devonian, and arranges them in his three sub-systems of the 

 Primordial, Lower, and Upper Silurian. If he is a palaeon- 

 tologist, he seizes at once upon the indisputable fact that 

 the general facies of the fossils of these three divisions, when 

 viewed in their collective aspect, has a marked character of 

 its own, wholly distinct from that of the faunas of the overlying 

 rock-groups. Profoundly impressed by this distinction, the less 

 striking differences between the faunas of the three members of 

 the Lower Palaeozoic itself dwindle in his eyes into utter insig- 

 nificance, and the slightest party bias is sufficient to lead him to 

 regard them with Barrande as forming " one grand and indivisible 

 triad which is the Silurian System." As discovery progresses, 

 gradually demonstrating the former presence of organic existences 

 in strata far below the base-line laid down by the founder of his 

 system, departing gradually in facies from his typical fauna (but, 

 nevertheless, connected therewith by almost imperceptible grada- 

 tions), his former admission, and the traditions of his school, compel 

 him to keep pace with it, extending his system and fauna down- 

 wards step by step. The result is, that if he is consistent, he is at 

 last driven to demand also, with Barrande, the inclusion of the beds 

 which Murchison, even in his latest years, acknowledged to be the 

 very basement rocks of & pre- Silurian system. 



If, on the other band, he is a stratigraphist, he instances the fact 

 that in Britain and America no general stratigraphical discordance 

 interrupts the vertical succession of formations between the Archean 

 and the Carboniferous. He points to the Llandovery beds of Britain, 

 and shows that the grandest stratigraphical break in the entire series 

 in the typical area occurs in the heart of a group of beds that the 

 founder of his school placed partly in one sub-system and partly in 

 the other ; but which he, in common with all scrupulous geologists, 

 included in a single formation, whose essential unity he fearlessly 

 challenges his opponents to deny. He calls attention to the Colonies 

 of Bohemia to show that even where the palaeontological distinction 

 between the sub-systems is most abrupt, yet, according to the 

 greatest of Silurian palaeontologists, there is actually an alternation 

 of the two faunas in the beds of passage. Or, he points triumphantly 

 to the succession in Scandinavia, where the Lower Palaeozoics are 

 reduced to a collective thickness of a few hundreds of feet, and are 

 occasionally folded up and entangled almost inextricably together in 

 a single section, and asks how is it possible to doubt the unity of a 

 System whose members are individually of such insignificant dimen- 

 sions, and, physically, are so indissolubly united ! 



The moving principle of the Sedgwickian, on the contrary, is the 

 demand for historic justice. With true British instinct, he recognizes 



