THE NAUTILUS. 



VOL. XV. AUGUST, 19O1. No. 4. 



PLATE II. 



Figs. 1, 2. Pleurodonte Adamsiana Clapp. This Journal for July, 

 p. 33. 



Figs. 3, 4. Pleurodonte Clappi Pilsbry. This Journal for July, 

 p. 34. 



Fig. 5. PhySa Walkeri Crandall. Petosky, Midi. 



Figs. 6, 7. Physa rhomboidea Crandall. Muddy Creek, Sedalia,Mo. 



Figs. 8, 9. Gastrodonta Clappi Pils. This Journal XII, p. 86; 

 XIV, p. 58. Large depressed specimen from Clingman Dome, no. 

 2490, coll G. H. Clapp. Alt. 3, diam. G.2 mm. 



Figs. 10, 11, 12. Nenia Smt'thise Pilsbry. Page 3'.. 



THE UNIONIDJE OF NOETH AMERICA. 



BY H. VON IHERING. 



By the publication of his " Synopsis'of the Naiades " Mr. Sirup- 

 son has rendered an excellent service to students of Malacology and 

 of the Unionidce especially. It is for me the greatest satisfaction to 

 felicitate Mr. Simpson upon having produced a work which will 

 mark a new period in the study of fresh-water mussels. 



It will be understood frorfk this that the work of Mr. Simpson does 

 not represent the conclusion of a serjes of successful studies, but a 

 basis for the beginning of a new period of investigation. Doubtless 

 this work will give an impulse to the study of the Unionidce, and 

 it is the purpose of these lines to point out what we may expect 

 concerning the American Unionida. 



