326 C. SCHUCHERT — LOWER HELDERBERG-ORISKANY FORMATIONS 



K.2S 



o >> 



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^ vieulopecten sp undet. 28042 



Pterinea cfr. flabellum (Conrad). 28043 



Mytilarca sp. undet. 28040 



Ct/i>ric(ir<Iiiii(( planulata Conrad 



indenta Conrad 



Conocardium trigonale (Phillips) 



Conularia near C. undulata Conrad 



Dalmaniies {Chasmops) anchiops (Green) 



(OdoiilocJicile) pleuroptyx (Green). 



Phacops cristala pipa Hall. 28053 



Proelus cra8simarginaius Hall 



Fish spine 



28052. 



From the Oriskany sandstone of Ontario, 71 species are now known, 

 and of these not less than 42 are also found in the Onondaga limestone 

 above. The close affinit}^ of this Oriskany fauna with that of the 

 Onondaga is made more apparent when it is noted that 36 species of the 

 71 constituting the Ontario Oriskany do not occur elsewhere, and that 

 31 of these are typical Onondaga limestone species. About half the 

 species restricted to the Oriskany of Ontario (36) are therefore earty in- 

 troductions of species characterizing the Onondaga limestone. Further, 

 a person collecting fossils in this region will find difficulty in distin- 

 guishing the Oriskany fossils, mainl}' corals, of the thin upper layers 

 from those of the Onondaga. 



That the Ontario Oriskany fauna is probably considerably younger 

 than the Upper Oriskany of New York or of the Appalachian region, is 

 also indicated by the absence of the Esopus grit in Ontario and the 

 many species common to it and the Onondaga cherty limestone. More- 

 over, of the 71 species found in Ontario, but 16 occur in the Lower Oris- 

 kany of New York, and but 8 Helderbergian species are present. These 

 figures, as thus stated, do not so forcibly bring out the fact of its younger 

 age as when it is remembered that 42 of the 71 species are also found in 

 the Onondaga limestone of the same region, while of the 56 species con- 

 stituting the New York Upper Oriskany fauna, but 11 are in the Onon- 

 daga and 30 are present in the Lower Oriskany. In other words, more 

 than half the New York Upper Oriskany species also occur in the Lower 

 Oriskany of the same state, while in Ontario about 60 per cent occur in 

 the Onondaga and but 20 per cent in the Lower Oriskany fauna. 



