184 NEW YORK STATE MUSEUM 



of the New Scotland fauna continues through the Becraft into the 

 Port Ewen. Only a few forms, such as Spirifer macro- 

 pleura, unable apparently to live in the slightly purer waters, 

 disappeared. 



Port Ewen beds 



The 200 feet included ih this formation are mostly concealed. 

 The few exposures are lithologically very similar to the New Scot- 

 land, varying from a dark blue limestone to a silicious shale. The 

 fossils are likewise very similar to those of the New Scotland, in- 

 cluding such typical forms as Strophe odonta becki, 

 Strophonella punctulifera, Streptelasma 

 strictum, Lichenalia torta and an abundance of 

 Coelospira con cava and Eatonia singularis. But 

 the transitional character of the Port Ewen to the Oriskany is 

 indicated by the presence of M e r i s t e 1 1 a lata and Spirifer 

 murchisoni. With the exception of these two fossils, all the 

 species found in these beds are Helderbergian. 



From the close of the Becraft to the uppermost Dalmanites 

 dentatus beds the fauna is transitional from the typical Helder- 

 bergian to the Oriskanian. The fauna acquires more and more an 

 Oriskanian aspect as the beds are ascended. Yet the lower beds con- 

 tain so many very typical Helderbergian species that there is no 

 hesitancy in placing these beds in the lower Helderberg. From the 

 upper 30 feet of these transition beds, however, the above mentioned 

 Helderbergian species are absent and there is a great increase of the 

 Oriskanian element. It was thought well, therefore, on account of 

 the very decided faunal change, to place these upper (D. dentatus) 

 beds in the Oriskany.^ The evidence for this is taken up in detail 

 under the lower Oriskany. 



Oriskany 



The Oriskany is mainly a silicious limestone with the silicious 

 content increasing perceptibly from the base upward. At times it is 



^Barrett likewise noted the close relationship of the fauna of the Trilo- 

 bite bed to that in the rocks above : " The relations of the Dalmanites 

 dentatus layer seem to be more with the rocks above than those below it" 

 Am. Jour. Sci. ser. 3. 45:72. 



