NORTH AMERICAN SPECIES OF THE GENUS ATAX 251 



try, although those so far made cover seven states, from New 

 York and Pennsylvania to Nebraska, and represent, all told, 

 forty-one localities — 2 in New York, 4 in Pennsylvania, 21 in 

 Michigan, 1 in Wisconsin, 4 in Illinois, 2 in Iowa, and 7 in 

 Nebraska. Material would be especially valuable from the 

 South and from the Pacific Coast, and it is hoped this paper 

 may be an incentive to investigators to take up the work of 

 collecting Hydrachnidse from those regions. Any material 

 sent to the writer will be gratefully acknowledged, and if de- 

 sired, labelled specimens returned; he will also gladly respond 

 to any requests for information concerning the group. 



Finally, the author would be doing an injustice both to those 

 who have very generously assisted him and to his own senti- 

 ments of grateful appreciation, did he fail to acknowledge that 

 assistance. To Dr. Richard Piersig of Leipzig, Germany, and 

 to Prof. F. Koenike of Bremen, he is indebted for literature, 

 and to Prof. Koenike also for specimens; each has been very 

 generous and to the kindness of each he acknowledges his in- 

 debtedness. Material has been received from Mr. R. A. 

 Johnson of Harvard University, Dr. R. H. Ward of Troy, N. 

 Y., Mr. Jas. B. Shearer of Bay City, Mich., Mr. M. Ricker 

 of Burlington, la., Prof. H. M. Kelly of Cornell College, la., 

 Mr. O. D. Noble of Linwood, Neb., and Prof. H. B. Ward 

 of the University of Nebraska, to each of whom the author ex- 

 tends his grateful acknowledgments. To Prof. Ward and to 

 his former teacher, Prof. J. E. Reighard of the University of 

 Michigan, he extends his thanks for many personal favors, and 

 he also acknowledges his obligation to Mr. Bryant Walker of 

 Detroit, Mich., for assistance in the identification of the mus- 

 sels collected. Finally, it is just and proper that he acknowl- 

 edge the assistance of his wife in the routine of the examina- 

 tion of mussels collected. He shall feel that he has partially 

 repaid his obligations to those mentioned if that which he 

 has accomplished by their assistance shall meet with their 

 approval. 



