670 NEW YORK STATE MUSEUM 



eastern America; but there is abundant evidence to show that 

 the species themselves have come into the gulf by the north- 

 west passage. 



Naples fauna 



This is the fauna of the Styliola limestone embedded in 

 the black Genesee shales and of the Portage beds of western 

 New York, ranging up to and beyond the summit of the original 

 Portage sandstones. The fauna is distinctly an invader from 

 the northwest. 1 It has almost naught in common with the 

 Hamilton fauna which preceded it on the ground, but is a con- 

 geries of oceanic organisms which together constitute the zone 

 ofManticoceras intumescens, well marked in many 

 parts of the world but nowhere with a more prolific fauna than 

 here. Eastward of Cayuga lake its integrity is lost by mergence 

 with the contemporaneous Ithaca fauna. The migration path 

 of this pelagic fauna has been traced toward the northwest 

 through Manitoba into Siberia, thence through Kussia into 

 Westphalia. Where it was originally autochthonal is not cer- 

 tain; perhaps Westphalia was its home, but in New York, where 

 its fauna became extensive, it was alien and short-lived. 



Ithaca fauna 



Contemporaneously with the Naples fauna in western New 

 York the Ithaca fauna held the field in central New York ap- 

 proximately, except in its latest stages, from Cayuga lake on 

 the west to the Chenango valley on the east. 



The Ithaca fauna is genetically sequential to the fauna of 

 the Hamilton epoch. Its species are at first identical with 

 those; then variations superinduced on these specific types man- 

 ifest themselves, and in the event the fauna in its totality is 

 clearly distinct from its ancestor. Hemmed' in on the east 

 by the barrier which made the Oneonta waters a lagoon, and 

 on the west by the invading Naples fauna, it found favorable 

 opportunity for multiplication and variation on ancestral 



x The authors of the preceding paper regard the Naples invasion as from 

 the Atlantic. This is an assumption unsupported by any evidence known 

 to the writer. 



