TYPICAL SHERBURNE . 431 



3. Camarotccchia congregata c 



4. G. proliflca ? rr 



5. Chonetes coronatus c 



6. G. setigerus r 



7. Schuchertella chemungensis var. arctostriata c 



8. Palcconeilo constrict a r 



9. Nyassa arguta rr 



10. Goniophora hamiltonensis rr 



11. Grammysia sp. rr 



12. Orthonota parvula ? rr 



13. Actinopteria hoydi c 



14. Glyptodes7}ia erecticm r 



15. TentacuUtes dellulus rr 



From its position below the Oneonta, it is highly probable that this repre- 

 sents the horizon of the Sherburne sandstones farther west. 



Albany County 



The carefully measured section up Bradt Hollow from the valley of 

 the Fox Kill at Peoria, in the township of Berne, Albany County, shows 

 some interesting facts. The shales and sandstones overlying the Onon- 

 daga carry Hamilton fossils for a thickness of between 1,415 and 1,720 

 feet, the exact amount not being ascertainable on account of the some- 

 what varying dip. Seventy-five feet above the top of the highest fossil- 

 iferous zone (Prosser, 38 B®) occurs the first horizon of red shales, 

 marking the beginning of Oneonta sedimentation. If we consider that 

 the Oneonta sedimentation has here entirely replaced the Ithaca, we must 

 hold at least 175 feet of the fossiliferous beds of Hamilton type as be- 

 longing to the Sherburne. This would reduce the thickness of the 

 Hamilton (inclusive of the Marcellus) to between 1,240 and 1,545 feet. 

 In the neighboring Schoharie Valley, where the Sherburne representative 

 retains its thickness of 250 feet below the Ithaca beds, the Hamilton 

 Marcellus is figured by Prosser as 1,685 feet.^° It must, however, be 

 borne in mind that such measurements are not absolutely correct, on 

 account of the variable dip of the strata. 



If the whole of the fossiliferous series in Bradt Hollow Hill is of 

 Hamilton age, then the red sedimentation (Oneonta type) has replaced 

 more than the upper half of the Sherburne. This is not improbable, since 

 in Ulster County the whole of the Sherburne and possibly some Hamil- 

 ton is replaced by this type of sedimentation. That is due to the fact that 

 that region is nearer to the source of supply of the continental sediments 

 which form the Oneonta-Catskill delta, and that hence these sediments 

 appear earlier in the geological column as we approach that region. 



20 Loc. cit., p. 190. 



