278 C. SCHUCHERT — LOWER BELDERBERG— ORISKANY FORMATIONS 



these types either have greater differentiation in species or the forms at- 

 tain a larger size. The fact that 9 per cent of the Helderbergian fauna, 

 pass into a generally accepted Devonic horizon, the Oriskany, outweighs 

 the evidence of a Siluric facies and specific derivatives. The writer 

 therefore concludes that the Helderbergian has a fauna unlike the 

 Siluric, hut one in harmony with the Devonic and its position near the 

 base of that system. 



Neither of the Helderbergian zones can be regarded as the deeper 

 water facies of the littoral Oriskany, not only because the fauna of the 

 latter has a more decided Devonic aspect, but also for the fact that 

 wherever the two formations are present the Oriskany always overlies 

 the Helderbergian. As far as known, there is no interlamination, and in 

 New York, where the stratification is simple, there is a regular sequence. 

 Where the older Oriskany is absent there is a slight unconformity between 

 the Helderberg and the later Oriskany. This unconformity becomes a 

 decided one in going from eastern to central New York, because the later 

 Oriskany gradually comes to overlie successively the various members 

 of the Helderbergian and finally the Cayugan. 



Table of the Helderbergian Fauna * 

 C - Ooeymans limestone; S = New Scotland beds; B — Becrafts limestone. 



Species with * are also in Siluric below. 

 Species with f are also in Oriskany above. 















M 

















o 









d 









Is 



CO 



d 







.5 



•r 







s 



o 







Ofi 



£3 







« 



o 







.zz 



o 







CQ 



•X' 







J> 



CO 





K*~> 



► 



ci 







S3 







o 



CD 



o 





M 



,_ 





© 



CD 



^ 



t 





2 



2 



£ 



CD 



E-i 



c 



^ 





O 





co 



'3 



j. 



CO 

 CD 



5 



CD 



a, 





cd 



S3 



c3 

 !s5 



i—i 



53 



73 



03 



CO 



Sponges, species. 

















Hindia fibrosa (Roenier). 10553, 17158, 20009, 

















27719. . . 



C8 

 s 



X 





X 



X 













s 















Kea ptcLculiies Infu/ndibuliforYnAs (Eaton) 



s 















" n. sp 



s 















Tschadites squamifer ( Hall). 27720 



s 







X 









* Nut including the Upper Ajrisaig, which is Siluric. Some of the Tennessee and Cumberland 

 species are knows from Hall's private collection. Numbers are of specimens in the United States 

 National Museum. 



