108 NEW YORK STATE MUSEUM 



the farther eastward one comes from the valley of the Chenango 

 riyer. Beyond the western limit of the sedimentation in that 

 region, we have the Sherburne sandstone representing the 

 opening stage of Portage time by a thickness of about 

 250 feet of arenaceons banks and shales, followed thereon by 

 600 to 800 feet of sandy shales carrying the peculiar fauna of the 

 Ithaca period, above which gradually comes in the fauna of the 

 true Chemung. Proceeding eastward again into the area cov- 

 ered by Oneonta-Catskill sediments, we find the lower portion of 

 these (Oneonta) encroaching on the upper portion of the Ithaca 

 marine deposits and westward of the Chenango river replacing 

 them in the succession, while still the marine Chemung fauna 

 comes in above them, -often preceded by slight reappearance 

 of the Ithaca fauna in its last stages. Beaching western Albany 

 county and the region of Bensselaerville, we find the Sherburne 

 sandstone thinned to 60 feet and immediately over it the shales 

 bearing no other fossils than the Estheria and twigs of 

 P s a r o n i u s (40 feet) while the red sediments of the Oneonta 

 Catskill above them evince a much earlier encroachment of 

 these brackish water deposits and the embayment in which they 

 were laid down, on the sea bottom where the marine fauna of 

 early Portage time had been for a while implanted. There is 

 no reason for separating these Estheria shales from the 

 base of the Oneonta; the fossils themselves are distinctively 

 of the character which indicates alliance with Oneonta sedi- 

 mentation, such creatures as one would expect to find asso- 

 ciated with the great Unio Amnigenia catskillenis, 

 and with the fishes of the Oneonta and Catskill; and we shall 

 probably do wisely to infer the incursion of Oneonta-Catskill 

 sedimentation into this section with the termination of the 60 

 feet of sandstone referred to the Sherburne. However we may 

 choose to construe this section, the fact remains that we have 

 here evidence of the Old Bed type of sedimentation emjihasized 

 by the presence of a most characteristic Old Bed species. No- 

 where else as yet has this species been seen in the rocks of New 

 York, but it occurs by hundreds in the locality cited, and its 



