BIGSBY PALAEOZOIC ROCKS OF NEW YORK. 371 



east by Clark ville to within two or three miles of the Hudson River. 

 From that place, the outer edge of this Scutella portion runs south 

 near Madison (?) to Kingston. It is well seen north of Cherry Valley 

 and through the townships of Warren and Columbia in the county 

 of Herkimer. 



The middle subdivision is coextensive with the upper. 



The lower subdivision is only visible eastward on the Helderberg 

 Range and from thence south-east and east to Kingston, and is a 

 prominent and well-characterized rock. It is not seen at Schoharie, 

 nor west of that village (Mather, p. 345). 



Position. — The same as the contiguous strata. 



Thickness. — It is 30-40 feet in thickness, and is thicker in South- 

 eastern New York than in Central New York. 



Fossils. — Fossils are finely formed here and abundant, although 

 they have not yet been fully described. 



Of Zoophyta, Bryozoa, Echinodermata, Dimyaria, and Gasteropoda, 

 it is only said by the New York geologists that they abound and be- 

 long mostly to the Niagara group. 



Out of 7 1 organic remains, of which we have some particulars, 58 

 appear to be original, 7 are derived, 6 transmitted, and 53 are typical. 

 But this is only true today. 



Upper Pentamerus Limestone. 



Mineral Character. — This stratum is distinguished from the last 

 only by greater compactness and some superadded fossils (De Vern. 

 loc. cit. p. 657), particularly by a smooth Pentamerus, similar in 

 shape to, but distinct from, P. galeatus. It contains several forms 

 of Atrypa, and according to Mr. Gebhard has a peculiar assemblage 

 of fossils, distinguishing it from the beds below. 



This second Pentamerus-limestone, according to Hall (p. 145), 

 rests immediately on the Encrinal or Scutella-limestone. It appears, 

 however, to be represented by Mather's second subdivision, 6, of the 

 Delthyris shaly limestone. 



Transition. — The four subdivisions, Waterlime, Lower Pentamerus 

 limestone, Delthyris shaly limestone, and the Upper Pentamerus 

 limestone, are found together as the result of one epoch by com- 

 munity of fossils and close mineral similarity. They are continua- 

 tions of the Niagara or Wenlock period, with such modifications 

 as we might expect. 



Fossils. — Our information here being limited, we anxiously await 

 the forthcoming volumes of James Hall, treating on the palaeonto- 

 logy of the strata above the Onondaga-salt group. 



From that able and indefatigable geologist, however, I only expect 

 more abundant illustrations of the equivalency of these four lime- 

 stones to the Niagara or Wenlock strata. 



Of the fossils enumerated as belonging to Lower Helderberg di- 

 vision, eleven are found in the Niagara group of New York, and 

 several others are of the English Wenlock and Ludlow periods. 

 None of them are seen below the Niagara group ; some, however, 



