56 THE HABITAT OF THE EURYPTERIDA 



to the land. Chamberlin says further that the eurypterids are found 

 in abundance in fresh-water deposits with only a few trails of annelids 

 suggesting marine conditions; they are assumed, therefore, to have 

 been marine first and then fresh water, but in this case also why may 

 we not consider that these forms were carried out to sea, rather than 

 that they lived in marine water? 



In direct opposition to this line of argument, Zittel in his Grund- 

 ziige der Palceontologie (327, 527) offers the following: "The Euryp- 

 terida are found associated with Graptolites, Cephalopods,andTrilo- 

 bites in the Ordovician of Bohemia* and North America; with marine 

 Crustacea (Phyllocarids and Ostracods) in the Silurian; with Ostra- 

 coderms and Arthrodires in the Devonian; and with land plants, 

 scorpions, insects, fishes, and fresh-water amphibians in the produc- 

 tive Coal Measures. It is apparent, therefore, that from being 

 originally marine forms, they became gradually adapted to brackish, 

 and possibly even to fresh water conditions." 



Clifton J. Sarle in 1898 discovered a new eurypterid fauna at the 

 base of the Salina, Middle Siluric, of western New York (240). This 

 formation had hitherto been considered particularly barren of fossils, 

 but Sarle found in two layers of the Pittsford black shales such an 

 abundance of eurypterids that some layers were "literally packed" 

 with their remains. The two shale beds are intercalated between 

 dolomite layers which, Sarle remarks, represented more open water 

 and were apparently unfavorable to the eurypterids. The occupa- 

 tion of the black shales by these animals "was apparently of com- 

 paratively short duration, merely an incursion, as it were, since the 

 black shale all told does not exceed 2 feet in thickness. The fact 

 that the eurypterids are often dismembered and their parts distri- 

 buted over considerable areas, and that a dozen or more are frequently 

 found side by side . . . . suggests that they may have been 

 drifted up by a current. On the other hand, the fine preservation of 

 much of the material, extending even to the delicate appendages, 

 shows that the currents were very weak, thus practically leaving the 

 animals in the position of death or molting" (240, 1086). 



A. W. Grabau in his Physical and Faunal Evolution of North 

 America during Ordovicic, Siluric, and Early Devonic Time (1909) 

 makes the facts of distribution an argument in favor of a fluviatile 

 habitat, thus calling attention to one of the most important aspects 



* No eurypterids have been found in the Ordovicic of Bohemia. This statement was not cor- 

 rected in the igio edition of the Grundiiige der Palaontolcgie, p. 568, but has been corrected in the 

 1913 edition of the Text-Book of Paltzontology, p. 779. 



