A STUDY OF THE UNIONID^E OF ARKANSAS, 

 WITH INCIDENTAL REFERENCE TO THEIR 

 DISTRIBUTION IN THE MISSISSIPPI VAL- 

 LEY. 



By R. Ellsworth Call, M. Sc, M. A., M. D. 



There exists very little published information concerning 

 the abundance, varieties, and geographic distribution of the 

 great molluscan family of Unionidce, within the limits of the 

 State of Arkansas. A few forms were originally accredited 

 to it ; some of these have not since been found in the State, 

 nor have some others ever occurred outside its boundary. 

 Of the mollusks of no other one State in the Union is less 

 known. 



During the progress of the investigation the results of 

 which are herein recorded, opportunity to consult a number 

 of original types has been afforded with some very interest- 

 ing results connected with the nomenclature of this great 

 group of mollusks. To those who have not had access to 

 original publications and to original specimens, much of the 

 synonymy herein developed will, perhaps, prove a matter of 

 surprise. The task which one thus assumes is not without 

 its share of responsibility. To do strict justice to those 

 most excellent early investigators, who so completely have 

 rendered all successive students their debtors, is no easy 

 task. That each one did the best he could, or knew, we 

 scarcely can doubt; measured by the faulty notions of species 

 that prevailed during their time they could, perhaps, for the 

 most part, have done little better. A half century spent upon 

 this great family by the veteran Dr. Isaac Lea must, in itself, 

 entitle his opinions to confidence and to weight. But author- 

 ity may never stand in place of Nature and in place of fact. 

 If so be a more modern notion of what constitutes specific 

 value, coupled with proper regard for environmental factors, 



