200 THE JOURNAL OF GEOLOGY. 



Prodtictns nebrascensis Owen. 



Prodtictiis longispinus Sowerby. 



Streptorhynchus crassus Meek and Hayden. 



These are plainly of Upper Carboniferous age. The limestones 

 cap the hills in that region, and spread over a great area, but fos- 

 sils were collected at this place only. 



Interchange of life between East and West. — The many beds 

 of marine fossils in the Productive Coal Measures are simply trans- 

 gressions from the western sea, and reach no further east than 

 Pennsylvania and West Virginia. The Appalachian system was 

 the western border of the ancient Atlantis^ which separated the 

 European from the Pacific waters, while the great Indo-Austra- 

 lian^ continent bounded the Pacific ocean on the south. This 

 ocean must have stretched from the American Coal Measures to 

 eastern China, the Salt Range in India, the Ural Mountains on the 

 borders of Russia, and into the Arctic regions, for we find related 

 faunas in all these places. Whatever we have of western Euro- 

 pean Coal Measure species must have migrated from this direc- 

 tion, since on the east there was no direct communication with 

 European waters. An example of this is Productus giga?iteus'^ 

 Martin, which is common in Europe, and is found in the Lower 

 Carboniferous of the McCloud river, Shasta county, but is not 

 found east of that place, unless P. latissinms Sowerby, from Mon- 

 tana, west of the main chain of the Rocky Mountains, be an 

 equivalent. 



On the other hand, many species seem to be confined to, or 

 characteristic of, this ocean ; among them may be mentioned 

 Productus cora d' Orbigny, which Waagen^ says is not found in 

 Europe, its nearest representative being Prodncttis riparius Traut- 

 schold ; it was however first described from South America. 



Goniatites mariamis Verneul is found in the Artinsk region of 



'SuESS: Antlitz der Erde, II., p. 17. 



^SuESS : Antlitz der Erde, II., p. 316. 



3 See Annual Report U. S. Geog. and Geol. Surv. Terr. 1883, Part I., p. 132, and 

 Bull. Geog. and Geol. Surv. Terr. Vol. II., No. 4, p. 354. 



-•Pal. Indica, Salt Range Fossils, Brachiopoda, p. 677. 



