480 GEOLOGY. 



ble number of species were common to it and to the northwestern 

 province, as also to the interior province after it had been invaded 

 by the Onondaga and northwestern Hamilton faunas. While its 

 fauna is not yet well enough known to sanction the drawing of final 

 conclusions, it bids fair to offer as fine an example of a steady 

 uninterrupted development of a provincial fauna as does the eastern 

 province of the fluctuating and militant development of a composite 

 fauna out of provincial invasions. 



The western fauna has, as now known, few salient features. The 

 corals which were present in considerable abundance were largely 

 identical or closely allied to those of the Onondaga fauna of the north- 

 east, and doubtless had a common origin, through some northern 

 connection. Brachiopods were, as might be expected, the leading 

 element. Several species were identical with those of the Onondaga 

 fauna, and several were identical with species embraced in the north- 

 western Hamilton fauna. The former are found mainly in the lower 

 horizons of the formation, and the latter in the upper. In this they 

 seem to indicate an early communication with the sources of the Onon- 

 daga fauna and a later connection with those of the northwestern 

 Hamilton. There were some pelecypods also that held a like rela- 

 tion, but the greater number seem to have been indigenous. Alto- 

 gether they were rather abundant. The same may be said of the 

 gastropods. The cephalopods, so far as known, were few and mostly 

 indigenous. The trilobites were feebly represented and were proba- 

 bly all indigenous. Echinoderms have not yet been reported. Fish 

 remains are found abundantly in certain localities. 



II. The Life of the Land Waters. 



Principle of interpretation. — It would doubtless be as difficult to 

 draw any sharp line between the fishes of the land waters and those 

 of the sea in Devonian times as it is now, even if we had as complete 

 knowledge of them, probably even more so, for the differentiation 

 of the two classes was doubtless less complete than now. For geo- 

 logical purposes, however, all those fishes that were denizens of the 

 streams and lakes, also those of the freshened waters of the estuaries, 

 bays, and inlets on the land border, may be classed together as fishes 

 of the land waters, for they were dependent on conditions inseparable 



