FOURTH REPORT OF THE DIRECTOR iQO/ 43 



Station on the West Shore Railroad. The character of the fauna 

 of these Port Ewen beds has not been well understood and it was 

 this problem that carried Professor Chadwick into the field. 

 Through the efforts of Mr Chadwick and Mr Shimer we have now 

 a fairly adequate idea of the composition of the fauna of these beds. 



Though, as already stated, the preponderance in the census of the 

 species so far as known, is Helderbergian there is a noteworthy 

 percentage of species that may be regarded as normal or at least 

 usual to the calcareous Oriskany above. Various others have been 

 recognized as passing upward from the Helderbergian into this 

 Oriskany and Mr Chadwick in his closest analyses of the assem- 

 blage has pointed out its generally decadent condition as a Helder- 

 berg fauna. 



There are also other species of very first import which have and 

 probably must continue to be regarded as index fossils of the 

 Oriskany formation. Chadwick determines Megalanteris 

 ovalis, Beachia suessana, Leptocoelia flabel- 

 lites, L e p t o s t r o p h i a oriskania, Brachyprion 

 m a j u s and B. schuchertanum. He indicates also the 

 possible occurrence of Spirifer arenosus. Professor 

 Shimer determines Spirifer m u r c h i s o n i and ^I e r i s - 



t e 1 1 a lata. 



It becomes now a question for very careful consideration whether 

 a fauna lying beneath the normal position of the Oriskany beds 

 and carrying such fossils as these, can with propriety be regarded 

 a Helderbergian fauna notwithstanding its preponderance of Helder- 

 berg species. Upon this line of inquiry the recently discovered 

 Oriskany fauna already referred to will throw additional light 

 but the evident earlier immigration into the eastern New York 

 region of Oriskany species than had before been noted is not in 

 anywise out of harmony with the evidence of their association 

 in the Gaspe basin at the northeast. 



Monograph of the Eurypterida. It has long been the writer's 

 purpose to prepare a revision of these remarkable crustaceans which 

 occur in a variety and abundance in the rocks of New York 

 unequaled elsewhere in the world. The Bertie \vatcrlime outcrops 

 in Erie, Cayuga and Herkimer counties and the Salina (Pittsford) 

 shales in Monroe and Orange counties have now afforded a really 

 extraordinary manifestation of the profusion of these creatures. 

 Fifty years ago James E. De Kay and Professor Plall had described 

 the commoner forms of these crustaceans Eurypterus and Pterygo- 

 tus from the Bertie waterlimcs, and Messrs Grote and Pitt some 



