II 



NOTE ON THE HABITAT OF THE EURYPTERIDS 



A large portion of the species described in the foregoing notes 

 are fossils from the Salina group (Pittsford shale and Bertie water- 

 lime). These had before been scattered in the collection and 

 neglected, because the eurypterids, synxiphosurans and crustaceans 

 of these formations focused all the attention of paleontologists on 

 their remarkable display. Nevertheless these modest brachiopods, 

 gastropods and pelecypods that are associated with the eurypterids 

 have an importance of their own in aiding us to arrive at a proper 

 conception of the habitat of the eurypterids. 



Clarke and Ruedemann in their monograph of the American 

 eurypterids 1 had arrived at the conclusion that the eurypterids were 

 originally marine, but that their climacteric fauna was euryhaline 

 or able to live in both very salt and brackish water and that their 

 later habit throughout the Devonian and Carboniferous led them 

 finally into the fresh water. This view has been challenged by 

 Prof. A. W. Grabau, 2 who has relegated them into the rivers from 

 earliest to latest Paleozoic time. His evidence rests mainly on the 

 summary of the distribution and occurrence of the eurypterids, fur- 

 nished for the same paper by Miss M. O'Connell. We have here 

 not the space to enter upon a discussion of his indirect evidence 

 and the attempt to dispute the direct faunal evidence furnished 

 by Clarke and Ruedemann in their memoir. The gist of his 

 argument is simply that the eurypterids are carried by the rivers 

 into the beds where they are found mingled with marine fossils. 

 Where the eurypterid remains themselves occur in great quantities 

 and are promiscuously mixed with graptolites, as in the Normans- 

 kill shale, or with graptolites, trilobites, "marine gastropods, etc., as 

 in the Schenectady beds, great importance is laid on the frag- 

 mentary condition of the eurypterid remains and the conclusion 

 therefrom derived that they are shed exoskeletons which drifted 

 down the rivers to meet the graptolites that were swept up from 

 the sea onto the mud flats. It is true that the exoskeletons of the 

 eurypterids are extremely fragmentary, even in formations where 

 they occur with all their growth stages and the animals were clearly 



1 The Eurypterida of New York. N. Y. State Mus. Mem. 14, 1912. 



2 Paleozoic Delta Deposits of North America. Geol. Soc. America Bui., 

 v. 24, no. 3, p. 4g8ff. 1913. 



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