Delation of eurypterids to environment 490 



method of attack by which further evidence is to be obtained. It is true 

 that, as Weller has said, ". ■ . . there is no inherent characteristic of 

 the fossil Eurypterus which can in any way suggest that it may not have 

 been a truly marine organism, and our conclusion that it was not such 

 an organism is drawn from the physical surroundings of the fossil itself, 

 rather than that the physical conditions are what we believe them to be 

 on account of some peculiarity of the fossil." 94 Still, Chamberlin's de- 

 duction, that the fish form "could only have developed in water that 

 possesses a persistent and usually rather rapid motion in a fixed direc- 

 tion — i. e., in rivers," must not be overlooked. Our investigations, how- 

 ever, must be directed mainly toward the physical characters of the strata. 

 It 'is precisely this close analysis of the physical characters of the strata 

 in which the Eurypterids occur, and the interpretation of these characters 

 in terms of origin, that has until recently been so universally neglected. 

 In the description of the species there has seldom been made an attempt 

 to locate them precisely in the formation, to note the state of their preser- 

 vation, and, above all, to note precisely their association or lack of asso- 

 ciation with other organisms. The fauna of a whole formation in which 

 Eurypterids occur has been listed, but as a rule one finds no statements 

 regarding the precise occurrence, whether other organisms occur in the 

 same stratum or whether they are restricted to higher or lower strata. 95 

 In order to get at the foundation of the problem, it has been necessary 

 to search the literature of the world to find out not only how many species 

 have been described, but also their conditions of preservation and their 

 association with other organisms. This work has been undertaken by 

 Miss M. O'Connell, a graduate student in paleontology in Columbia Uni- 

 versity. She has prepared an abstract of her studies which, though in- 

 complete, embodies all but the rarest occurrences in this field. Miss 

 O'Connell has continued this investigation and endeavored by the study 

 of the museum material, as well as the literature, to trace out, so far as 

 is possible, the precise habitat of the Eurypterids. Her results will be 

 published in the near future. 



Distribution mid occurrence of the Eurypterids: Summary by M. 

 O'Connell — In general. — The world-distribution of the Eurypterids shows 

 that these merostomes ranged in geological age from the pre-Cambric 

 through the Permic, reaching their acme in numbers, development, and 

 diversity of types in the Siluric. From a careful search through the 

 literature of Europe and America it was found thai K genera and suh- 



04 Bull. Geol. Soc. Am., vol. 22, 1911, p. 228. 



B5 This criticism also applies, though to a loss extent, to the magnificent memoir on 

 the Eurypterids of New York jnst issued by the Survey of thai state. 



