184 NEW YORK STATE MUSEUM 



physical barriers that were interposed to lines of migration. Means are at 

 hand in very many cases for distinguishing between free swimming inhabit- 

 ants of the open sea and other forms whose structural organization proves 

 them to have been bottom feeders, mud grovelers, or frequenters of estu- 

 aries and fresh-water lagoons. Manifestly inferences of this nature are of 

 far-reaching geological significance, besides having a direct practical appli- 

 cation. Finally, a knowledge of the relations of successive vertebrate 

 faunas is an important corollary to the information we have concerning 

 fossil invertebrate faunas, the two categories being mutually complementary, 

 and taken together are essential to a natural classification of geologic 

 formations. 



We may consider first some of the more general conclusions derived 

 from a study of the distribution of Devonic fishes, having special reference 

 to those of New York State. In the first place it is necessary to bear in 

 mind that the Devonic faunas of the interior of North America announce 

 themselves as belonging to two distinct types, one being more or less con- 

 fined to the eastern, and the other to the west central United States and 

 Canada. Or, to put it differently, it is possible to recognize within the 

 interior of our continent two more or less distinct geological provinces of 

 the Devonic, differing from each other and from the more remote areas 

 lying to the westward (Cordilleran and continental border provinces) in 

 their respective faunal characteristics. The eastern interior province, which 

 has received the name of Appalachian, is typically represented in New York 

 State, but extends westward into Ontario and Michigan, and southwestward 

 into the Ohio valley region, forming circumscribed areas known as the 

 Cumberland and Indiana basins. The western interior province is repre- 

 sented typically in Iowa, and was more or less effectively separated from 

 the eastern during early and Middle Devonic time. Its limits are coex- 

 tensive with the so called Dakota sea, which was open to the northwest 

 during the mid-Devonic through Manitoba, the Mackenzie Basin, and across 

 Behring straits into Siberia, but was probably closed to the northeast. The 

 suggestion has been made, and indeed been received with some favor, that 



