58 H. 8. Williams — Different types of the 



whole eastern Devonian and is plainly a sequent to an under- 

 lying upper Silurian fauna. It is followed by a Carbonif- 

 erous fauna to which it is generically closely related, and about 

 its border is terminated by a black shale. 



4th. A western area represented by a massive thick series 

 of limestones followed by black shales, not separated into 

 distinct faunas, but carrying a common fauna showing but 

 slight change from bottom to top. 



With all these great contrasts in lithological, stratigraphi- 

 cal and paleontological characters the evidence is satisfactory 

 that the several sections are representatives of the same geo- 

 logical age ; that, taken as wholes, they do not represent 

 parts, the one taking the place of an interval in the other, but 

 they cover approximately the same interval, and probably rep- 

 resent approximately the depositions of the same length of 

 geological time. 



They are bound together, and their relationship certified to 

 by the fossils they contain. The relationship is recognized 

 in the combination of species to form faunas and in the vari- 

 etal modification of species, as well as in the identhry of the 

 species themselves. We cannot find stronger contrasts across 

 the Atlantic eastward than are found across the continent 

 westward. The principles which the American geologist is 

 required to apply in discussing the geology of his own do- 

 main are no less broad than those which the International 

 Congress meets with when it attempts to unify nomenclature 

 for all the world. Wherever unification is practicable in Amer- 

 ica it is practicable for all the world, and where America finds 

 unification a cumberance it is useless for an International Con- 

 gress to attempt it. 



What is there in the Devonian system, as represented in 

 North America, which demands uniformity of nomenclature, 

 and wherein will attempts at uniformity in nomenclature 

 either strain or misrepresent the facts ? 



1st. It is perfectly clear to a paleontologist studying the 

 faunas and floras, that the system under consideration, in each 

 of the so dissimilar types, is the representative of the Devonian 

 system of Great Britain, Belgium, Germany and Russia, in all 

 the central features of its marine and brackish invertebrate, 

 and vertebrate faunas, and in its floras. That the name Devo- 

 nian, as the first name used, should be applied to this system 

 of rocks, we see no reason for dispute. 



2d. In all the sections, in so far as they exhibit it, the order 

 of sequence in the modification of faunas is the same, and this 

 sequence as presented in foreign sections is found to follow 

 the same order, wherever species are identical, or are closely 

 allied varieties of the same type ; their place of dominance in 



