THE NAYADES (FRESHWATER MUSSELS) OF THE 



UPPER TENNESSEE DRAINAGE. WITH NOTES 



ON SYNONYMY AND DISTRIBUTION. 



By a. E. ORTMANN, Ph.D., Sc.D. 

 (Read April 19, 19 18.) 



The present enumeration of the mussels of the upper Tennessee 

 is the result of the writer's work carried on in this region since 1912, 

 under the auspices of the Carnegie Aluseum of Pittsburgh, Dr. W. 

 J. Holland, director. 



It is intended, herein, to give a complete synopsis of this fauna, 

 using the modern system, and the accepted rules of nomenclature, 

 together with a full synonymy of the various forms, as far as it has 

 been firmly established. Much stress has been laid upon the facts 

 of the geographical distribution, because it has become evident that 

 not all of the species are uniformly distributed in this area. 



The latter includes all of the upper Tennessee drainage from 

 Chattanooga, Tenn., upward, comprising largely eastern Tennessee, 

 a small section of northern Georgia, and parts of North Carolina 

 (in the high mountains), and southwestern Mrginia. It appears 

 that the Walden Gorge of the Tennessee River, below Chattanooga, 

 forms some kind of a barrier to Nayad distribution, at least for cer- 

 tain species ; at any rate, it forms a natural division within the Ten- 

 nessee system. Of course, not all parts of this drainage have been 

 investigated by myself; but collections have been made in all of the 

 more important streams ; and, together with the records obtained 

 from other sources, it is believed that this fauna is now rather com- 

 pletely known. 



The region in question is known as one of the chief centers of 

 Nayad development, and may be called the most prolific section of 

 the world in this particular group. Alany of the species described 

 by the older authors (Conrad, Lea, and others) originally came 

 from this region. But no synopsis of the whole fauna has been pub- 

 lished, except the attempt made by Lewis (1871 and 1872). 



PROC. AMER. PHIL. SOC. , VOL. LVU. II, SEPT. 30, I9I8. 521 



