COMPOSITION AN'D RELATIOXSHIPS OF THE FAUXAS 



463 



Table VI. — Composition and Relationships of Western (typical), Central, and 



Eastern Ithaca Faunas 



Species, 



, , , .thacaof Chenangfo Ithaca east of 



Ithaca of Ithaca re- and C o r t 1 a n d Ch enangro Val- 



gion. 



counties (Clarke i 



Number 



of 

 species. 



ley ( Prosser ). 



Percent- 

 age. 



Number 



of 

 species. 



Percent- 

 age. 



Number 



of 

 species. 



Percent- 

 age. 



Total number of species, 

 excluding those doubt- 

 fully identified 107 



Hamilton species 39 



Naples species 9 



lowan species 3 



New or Ithaca species.. 56 

 New varieties of Ham- 

 ilton species 



Chemung species, not 

 recorded from Ithaca 

 fauna 



100.00 



86 



100.0 ; 



102 



100.0 



36.45 



60 



69.77 i 



83 



81.38 



8.40 



7 



8.14 i 



2 



1.96 



2.80 



3 



3.49 1 







0.00 



52.. 35 



10 



11.63 ! 



12 

 2 



11.76 

 1.96 





6 



6.98 



3 



2.94 



This comparison very clearly shows that the Ithaca fauna west of the 

 former Sherburne bar — that is. in the region of the ancestral home of 

 the Ithaca fauna — is modified only to a moderate degree by the immi- 

 grant Hamilton fauna from the east (or the persistent Hamilton types 

 within the Ithaca basin) . The Hamilton element constitutes only 36.5 per 

 cent of the whole of the Ithaca fauna in the type region^ while nearly 52.5 

 per cent of the fauna are new types, developed in situ from the preceding- 

 Hamilton fauna. In the eastern region, however, the fauna of the Ithaca 

 beds is still largely a Hamilton one, species of that type constituting 

 83 1/3 per cent of the whole,^- while only 16 2/3 per cent are immigrant 

 Ithaca and Naples species from the Ithaca region. ^^ The central region 

 is iutermediate, showing about 70 per cent Hamilton and 18.6 per cent 

 Ithaca.^* An inspection of the larger table, III, will show that, with 

 few, almost negligible, exceptions, the immigrants from the western area 

 are confined to, or at least most common in, the more westerly portion of 

 the eastern region — that is, that nearest the home of the Ithaca fauna. 

 It is also apparent that, whereas in the Ithaca region nearly 8.5 per cent 

 of the Ithaca fauna consists of Naples species and 2.8 per cent of lowan 

 species, the eastern Ithaca fauna has only about 2 per cent of its total 



31 This includes the 18 species which make their first appearance in the Sherburne or 

 Lower Portage of the Ithaca region. 



'- IncUiding the two new varieties of Hamilton species. 



33 This includes the three Chemung species not yet reported from the Ithaca, but 

 probably occurring there. 



3+ This includes the six Chemung species not yet recorded from the typical Ithaca. 



