THE NAIADES OF MISSOURI. 



{Plates i — xxviii.) New Series. 



Introduction. 



After some years of intensive studies in the field, library and 

 laboratory an attempt is made to give a catalogued account of 

 the Naiadss, or Fresh-water Mussels, of Missouri. Most of the 

 data for this descriptive and illustrated catalogue have been 

 collected through extensive, personal surveys of the most import- 

 tant streams and lakes of the State and now the typical anato- 

 mical and shell material from the different localities are pre- 

 served in the writer's laboratory. No literature of any conse- 

 quence, dealing with the Naiades of Missouri, had been produced 

 until the author of this paper made a preliminary report on 

 "The Mussel Resources of Missouri." This was, however, a 

 government report, published for economic purposes, the detailed 

 account of the scientific observations of which will not appear 

 until a later date. 



The plan of classification, based on anatomical structures, 

 notably those of mar-supial characters, has been carefully followed 

 in this work. The many changes in the nomenclature of this 

 catalogue from that of the vSimpsonian system are due especially 

 to the recognition of Lindahl's orthographic modification and of 

 the wise scheme of taxonomy for the Naiades begun by Sterki 

 (1906) and well consummated by Ortmann (1912) ; and also to the 

 acceptance of Rafinesque's priority as recently revived by Mr. 

 Frierson and accepted by Dr. Ortmann. The writer believes 

 that the ultimate taxonomic system will be based far more upon 

 the anatomical structure of juvenile and adult than upon their 

 shell characters from the fact that the soft parts are more constant 



