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gunk grit at Otisville, Orange county, an assemblage of eurypterids 

 remarkable for its profusion of immature growth stages. This 

 fauna, lying far to the east of all previously known occurrences of 

 those creatures, was described in a preliminary way by the writer. 

 Still more recently, indeed since the preparation of this book was 

 believed to be completed, the field investigations of Doctor Ruede- 

 mann have brought to light a large and new fauna in the Lower 

 Siluric (Frankfort) shale rather widely disseminated in the lower 

 Mohawk valley; this constitutes the very earliest assemblage of 

 these merostomes in conditions which indicate that they formed a 

 colony of long local duration. 



The collections which have thus been brought together from the 

 productive localities mentioned for the preparation of the present 

 treatise have been really great ; indeed they represent some thou- 

 sands of specimens and it is quite within reason to say that no series 

 of the Eurypterida of equal size and variety has ever before been 

 a— embled. It is quite as true that no equal area in the world has 

 proved as fruitful in the quantity and diversity of these organisms 

 as the State of New York. Through the courtesy of many corre- 

 spondents and museums much material from outside of New York 

 has been placed at the demands of this work: the species of 

 the Kokomo waterlimes of Indiana; of the Cambric Strabops of 

 Missouri; the Siluric Megalograptus of Ohio and the Carbonic 

 Hastimima of Brazil and New Brunswick ; in all, I believe, an 

 unexampled array of these extinct arachnids. 



The work of elaborating these earlier studies and expanding 

 them into this fuller form has very largely depended on the aid of 

 Dr Rudolf Ruedemann who has brought to the work keen analytical 

 powers, a broad grasp of its problems and an enthusiastic assiduity. 

 I fully realize and gladly express my obligation to this assistance 

 and desire that the interested reader accord to my coworker ade- 

 quate acknowledgment of his efficient part of this work. 



The treatise itself seems to carry its own justification; aside from 

 the close analysis of structural details, there are chapters on ontog- 

 eny, phylogeny, on life habits and conditions as well as on organ- 

 ization which, though possibly not beyond criticism, are at least 

 informing and constitute an advance of knowledge. 



To the following individuals and institutions the authors have 

 been indebted for aid : 



The Buffalo Society of Natural Sciences, through its board of 

 trustees and its superintendent, Mr Henry R. Howland 



The American Museum of Natural History, through Dr E. O 

 Hovey and the late Prof. R. P. Whitfield 



The United States National Museum, through Drs R. S. Bassler, 

 E. O. Ulrich and David White 



The Smithsonian Institution, through Secretary Charles D. W r al- 

 cott 



Columbia University, through Prof. A. W. Grabau and Jesse E. 

 Hyde 



