EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 131 



beds. These writers regarded this unit as pertaining to the Helderbergian 

 group. In Memoir 3 the thickness of these beds was given in a section at 

 Rondout measured by Messrs van Ingen and Ruedemann as 225 feet and a 

 fauna was determined which contained only species of the Helderbergian 

 units beneath. These determinations are indicated in the summary list of 

 the fauna given below. The distinctive characters of the Port Ewen forma- 

 tion in this section have been excellently described by van Ingen [N. Y. 

 State Mus. Bui. 69] and he. too in his species list cited no fossils which 

 could be regarded as other than surviving Helderberg species. Mr Chad- 

 wick's field of observation has covered not only this but a more extended 

 region southward. His studies involve a reexamination of the type section 

 with additional sections at Cottekill, on Catskill creek and elsewhere. . He 

 has brought together a list of the leading species in the basal beds of the 

 Port Ewen formation in which he has determined not only a much larger 

 number of species than before known, but among them finds a noteworthy 

 percentage of species that may be regarded as normal to the calcareous or 

 Becraft Oriskany. Various others have been recognized as passing upward 

 from the Helderbergian into this Oriskany and in his close analyses of the 

 assemblage Mr Chadwick points out its decadent condition as a Helderberg 

 fauna. Mr Chadwick's studies have not as yet extended to the exact 

 determination of the higher faunas. Mr Shimer's determinations of the 

 Port Ewen fauna at Port Jervis include the species Spirifer murchi- 

 soni, Meristella lata, forms entirely diagnostic of the Becraft 

 Oriskany. 



The following table presents the sum of our present knowledge of the 

 Port Ewen fauna, the letters before each name indicating the responsible 

 authority for the determinations (C = Clarke, Ch = Chadwick, G = Grabau, 

 S = Shimer, V=van Ingen) and indicates the range of the species from the 

 Helderbergian below and upward into the Oriskany; also their representa- 

 tion in the eastern Atlantic faunas of this time. 



