ORTHOCERAS IN THE ONEONTA BEDS OF CHENANGO VALLEY 171 



mud and the later chambers filled with gases of decomposition, 

 the erect position of the shells, maintained continuously while 

 the sedimentation went on about them, would naturally be as- 

 sumed. 



In the flagstones appearing throughout the quarry region in 

 the vicinity of West Hurley, Ulster co., evidence of similar occur- 

 rences of vertical Orthoceras has been observed. Doubtless 

 the greater part of the entire mass of these flagstones, which ac- 

 cording to the estimate made by N. H. Darton are not less than 

 4000 feet thick, represents physical conditions quite similar to 

 those evident in the rocks of the Chenango valley, conditions 

 which here are completed and terminated only with the termina- 

 tion of the Catskill formation. Some of the evidences of the 

 vertical Orthoceras from these rocks are conclusive, though 

 in respect to abundance and mode of preservation they are less 

 impressive than the occurrence at Oxford. In association with 

 these organic remains are, however, often found formations of 

 similar appearance, likewise crossing the strata vertically, fre- 

 quently of small size, and when the rock is schistose, showing 

 concavities on one side and convexities on the other side of the 

 slabs. The majority of these are doubtless of mechanical origin, 

 perhaps in part representing vertical tubules or vertical disturb- 

 ances of straticulation by the bubbling of confined gases or air 

 up through the sediments. 



