130 Evolution and Distribution of Fishes 



of a land vegetation, we are forced to conclude that the 

 Upper Cornlferous of the Middle Devonian was of fresh- 

 water origin, unless weighty arguments to the contrary can 

 be adduced. 



But undoubtedly a mixing of lists of fossils, from closely 

 placed beds or laminae, some of which were of marine, 

 some of freshwater origin, has frequently taken place for 

 Ohio. Thus the recording of Lingula and Discina with 

 fish remains, while perhaps rarely indicating rapid changes 

 in the relation of sea and land, is accurately and readily 

 explained by the more recent studies of C. S. Prosser 

 (5^:297) on "The Sunbury Shale of Ohio," where he 

 shows that only fish remains occur throughout one bed, 

 while the above-named brachiopods are found abundantly 

 at the base of the bed where change was proceeding. They 

 are 7iot mixed together. 



As Whiteaves and Eastman have pointed out, a wide 

 extension of this series of beds, with similar fish-remains, 

 was continued into Hudson's Bay {8g: 191), and on p. 193 

 he shows the close resemblances of the strata there to the 

 Eifelian deposits of Bohemian and Russian Central Europe. 



During deposit of the Huron and Hamilton shales and 

 limestones, the sea again encroached at least in some areas, 

 and this period marks the transition from a Mid to an 

 Upper Devonian fish fauna. So when land elevation again 

 took place, and freshwater conditions were reestablished, 

 deposits over extensive areas of rocks with contained fish- 

 remains, were laid down, that extend westward from New 

 York and Pennsylvania through Ohio to Iowa and Colo- 

 rado. These form the Catskill and Cleveland series. The 

 abundance and rich variety of this Upper Devonian Fish 

 Fauna is demonstrated in the lists given by Claypole for 

 Ohio (57:318) and by Eastman generally (op. cit. pp. 24- 

 172). Thus the former lists fully a hundred species from 

 the Ohio shales. For the New World as for the Old there- 

 fore, this period was evidently the one when fish-life was 

 dominant and prodigiously abundant in freshwaters, though 

 — so far as exact evidence goes — was wholly or almost 

 wholly absent from the sea. 



