50 NEW YORK STATE MUSEUM 



shaped fishes among races which have not progressed, the origin of 

 the paired fins and the development of the effective fins. The chap- 

 ter entitled " Geological conclusions " is of special interest as indicat- 

 ing the distribution and migrations of the early fish fauna and may 

 well be reproduced here. 



GEOLOGICAL CONCLUSIONS 



It will be convenient to include under this head certain topics 

 whose practical bearing is of chief interest to the geologist, although 

 the evidence involved is partly zoological, and in still larger part 

 geographical, or paleogeographical. We refer to such matters as 

 relate to the areal and vertical distribution of Devonic fish life, the 

 dispersion of new types and varieties, migration, succession and 

 occasional recurrence of faunas, and indications furnished by the 

 fossils themselves in regard to climatal and physical conditions, 

 either those of local nature, or others prevailing over wide areas. 

 Thus, by way of illustration, we are able to affirm from the general 

 complexion of ancient faunas, that the climate of arctic regions was 

 notably warmer during the Devonic and late Paleozoic than at sub- 

 sequent periods. We are in possession, also, of a large fund of 

 evidence regarding migrational movements, and can delineate with 

 great exactitude a number of physical barriers that were interposed 

 to lines of migration. Means are at hand in very many cases for 

 distinguishing between free swimming inhabitants of the open sea 

 and other forms whose structural organization proves them to have 

 been bottom feeders, mud grovelers, or frequenters of estuaries and 

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

 far-reaching geological significance, besides having a direct practical 

 application. 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 altogether 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 bein^ more or less confined to the eastern, and the other 

 to the west central United States and Canada. Or, to put it diflfer- 

 ently, it is possible to recognize within the interior of our continent 

 two more or less distinct geological provinces of the Devonic, 

 difiFering: from each other and from the more remote areas lying to 

 the westward (Cordilleran and continued border provinces) in 

 their resoective faunal characteristics. The eastern interior prov- 

 ince, which has received the name of Appalachian, is tvpically 

 represented in New York State, but extends westward into Ontario 

 and Michigan, and southwestward into the Ohio valley region, 



