514 C. SCHUCHERT PALEOGEOGRAPHY OF XORTH AMERICA 



south side of the mineral axis of the Cumbrian mountains. A small part of 

 the slates of Cornwall and South Devon. ? A part of the slate series of the 

 Isle of Man, etcetera. 



"2. Upper Cambrian system. — A large part of the Lammermuir chain on the 

 south frontier of Scotland. A part of the third Cumbrian group, commencing 

 with the calcareous slates of Coniston and Windermere. The system of the 

 Berwyns and South Wales. The slates of Charwood forest. ? All of the 

 North Devon and a part of the South Devon series. The greater part of the 

 •Cornish series. 



"3. The Silurian system. — The upper part of the third Cumbrian group, 

 chiefly expended in Westmoreland and Yorkshire. The flagstone series of 

 Denbigshire. The hills on both sides of Llangollen. The region east of the 

 Berwyn chain. The regions described in the papers of Mr Murchison, from 

 which the types of the system are derived. The lowest part of the culmiferous 

 series. ? 



"Over all the preceding comes the Old Red Sandstone" (685). 



From the foregoing definitions, it is clear that Paleozoic originally em- 

 braced the f ossiliferous formations beneath the Old Eed sandstone — that 

 is, the continental phase of the marine Devonic, to and including the 

 ""Cambrian." This base, then, was a very uncertain one, and included 

 Proterozoic rocks, as this term is now understood. In other words, Paleo- 

 zoic, as originally defined, comprised in the main what now belongs to the 

 fossiliferous systems — Cambric, Ordovicic, and Siluric. As for the non- 

 fossiliferous deposits also included, these may here be set aside. 



Protozoic, as the type areas on which this term was based are now com- 

 prehended, certainly embraced a considerable portion of the equivalent 

 formations included under Paleozoic, and also much that is now referred 

 to the Proterozoic. The words "the series generally without organic re- 

 mains" might easily be made to apply to the generally unfossiliferous 

 Proterozoic era. It is there evident that this term is a very vague one — 

 a sort of "dump box," in fact, into which all the unresolved formations 

 were then thrown. Hence there is no need of reviving the term, nor 

 should it displace the names far better defined — Proterozoic and Paleozoic. 



Since Sedgwick's use of the term Paleozoic, it has been extended to em- 

 brace all the systems above the Proterozoic and beneath the Mesozoic. In 

 recent years, however, the great significance of the Taconic revolution has 

 been recognized in America, and in 1895 Dana thought it advisable to 

 separate this era into two "sections," as follows : 



"Paleozoic time is naturally divided into two sections at the break between 

 the Lower and Upper Silurian. This boundary line is marked in the history 

 by an epoch of mountain-making in eastern North America and western Eu- 

 rope, and by a somewhat abrupt transition in the animal life of the seas. . . . 



"The first of these sections, the Eopaleozoic, was characterized by the fact of 

 almost universal seas over the continental area, and of universal marine life, 

 and also by the more specific Paleozoic fact, that marine invertebrates . . . 



