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NEW YORK STATE MUSEUM 



have wandered into the shallow waters where Schoharie sedi- 

 ment was depositing; they may have, on the other hand, come 

 in from some source, northeast or southeast, as yet unknown 

 to us. and hence be related ancestrally to similar forms of the 

 overlying Onondaga limestone. Present evidence seems to favor 

 the former conclusion without disparagement to the genetic re- 

 lations of these cephalopods to those of the Onondaga. It seems 

 justifiable however to assert that the fauna of the Onondaga 

 period as a whole, with its noteworthy coral, trilobite, cephalo- 

 pod and gastropod facies unequally developed locally, is a com- 

 plex congeries, largely from the western reaches of the Ap- 

 palachian gulf, but freely inoculated with elements genetically 

 from the northeast. The latter may have come in directly, 

 geographically and genetically, through the Oriskany province 

 of eastern New York or indirectly into the western limestones, 

 after migration from New York southward to the end of the 

 barrier and thence into the heart of the gulf. The latter seems 

 specially probable of the gastropod element. 



As the eastern waters cleared, the new fauna could migrate 

 eastward and so become the Schoharie fauna. At this time a 

 channel which extended northward along what is now the 

 Connecticut valley and thence by way of the St Lawrence 

 to the North Atlantic formed au outlet for the Onondaga sea 

 to the northeast. Since black mud strata were deposited in this 

 channel till Schoharie time, no migration of pure water species 

 from the Atlantic could take place till just before the beginning 

 of Onondaga time. But with this channel open, Eurasian types 

 which had migrated along the shore of "Atlantis?', a North 

 Atlantic continent, could enter the Mississippian sea of eastern 

 North America. Schuchert believes that a portion of the Onon- 

 daga fauna at least came into the interior sea by this channel, 

 while another portion came from the Brazilian region by way 

 of the southern or Indiana channel. It seems not unlikely that 

 the (-cplm lojjod element of the Schoharie entered the Appalachian 

 gulf from the northeast by the Connecticut channel, and mi- 

 grated westward, appearing either as the same species or in 

 modified form in the Onondaga of the western region. The same 

 thing appears to be true of the trilobites, though some as 

 C a 1 y m m e n e plat y s appear earlier or at the same time in 



