FOURTH REPORT O? THE DIRECTOR I907 5 1 



forming circumscribed areas known as the Cumberland and Indiana 

 basins. The western interior province is represented typically in 

 Iowa, and was more or less effectively separated from the eastern 

 during early and Middle 'Devonic time. Its limits are coextensive 

 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 re- 

 ceived with some favor, that intercommunication existed during 

 the mid-Devonic between the typical lowan and Eurasian faunas 

 by means of a northeasterly passageway through Manitoba, Hudson 

 and James bays, Greenland, Spitzbergen and circumpolar regions. 

 More recently, however, weighty objections have been opposed to 

 this theory, and it has been asserted very emphatically by Professor 

 Schuchert that there is not the slightest reason to connect the Hudson 

 and James Bay Devonic with that of the Dakota sea (or western 

 intercontinental province). It is further denied by the same author 

 that this latter province was in connection with a southern ocean, ex- 

 tending into Brazil, until Hamilton time. On the other hand 

 students are agreed that communication was maintained between 

 the Appalachian province and that of the southern hemisphere 

 during the mid-Devonic. Concerning the pathways that were open 

 between the Appalachian and Eurasian provinces during the Middle 

 and later Devonic there are still some differences of opinion. 



It will be observed accordingly, that the Devonic in this country 

 was preeminently an era of provincial development of marine 

 faunas. Furthermore it appears that diversity in this respect is 

 more strongly marked in the Appalachian region, where there were 

 varying conditions of sedimentary deposition, than in the Cordilleran 

 and continental border regions, where these conditions were more 

 uniform. Thus, in the eastern province, as Professor Williams has 

 pointed out, diversity and alternation of deposits are accompanied 

 by numerous successive and distinct faunas ; in the extreme western 

 regions, uniformity of prevailing calcareous sedimentation for long 

 periods is characterized by the abnormally long continuance of many 

 Devonic species ; and the central , continental province, midway 

 between the two, is marked by the unmistakable recurrence of 

 Devonic species well along into the Carbonic. Another noteworthy 

 feature of the Devonic which has been developed very fully and 

 clearly by the painstaking investigation of Dr Clarke is that fauna! 

 changes within the ancient Appalachian sea are sometimes so pre- 

 cisely indicated that it is possible, as in the case of the Portage 

 group, to trace the boundaries not only of local provinces, but of 

 local subprovinces characterizing the sta.ije in question. Thus, the 

 Genesee province of the Portage is divided into Chautauquan and 

 Naples subprovinces on the basis of differences in their faunal 

 fades; and an interesting peculiarity of the Naples subprovince is 

 that, as stated bv Dr Clarke " with contemporaneous faunas of the 

 Appalachian gulf" its fauna "has in its purity no organic relation, 

 direct or sequential." 



