522 ORTMANN—NAYADES OF 
In this connection it should be noted that Lewis’s ‘‘ Holston 
’ 
River” actually is the Tennessee River below Knoxville (chiefly in 
the region of Concord). Indeed, even at present, the natives in Con- 
cord call the river there “ Holston”; but the maps of the U. S. Geo- 
logical Survey give the name Tennessee to the river below the junc- 
tion of the Holston (proper) and French Broad. In Knoxville the 
river is called Tennessee. 
Aside from Lewis’s paper, only a few are at hand which con- 
tribute to the fauna of this region. One of them has been published 
by Pilsbry and Rhoads (1896). This is, however, by no means a 
synopsis, containing hardly half of the forms which are found here. 
But on account of the good locality-records it is very valuable; in 
fact, it is, up to the present time, the most accurate publication in 
this respect. And further, two preliminary papers have been pub- 
lished, based upon my own collections; one by myself (Ortmann, 
19130), the other by Goodrich (1913). . These, however, treat only 
of the headwaters-region of Powell, Clinch, and Holston in Virginia. 
In addition to the material collected by myself, I have examined 
the upper Tennessee shells in the collection of Mr. B. Walker in De- 
troit, and I want to express to Mr. Walker my best thanks for the 
privilege of examining his shells, and the delightful days I spent in 
his home in April, 1916. Mr. Walker has a great number of shells 
from this region obtained from older collections, which in part are 
cotypes, topotypes, or other authentic material. But the greatest 
treasure in his collection are the Nayades collected by Professor Dr. 
C. C. Adams in 1899 to 1901, in the course of his work on Jo, be- 
cause Professor Adams always was very careful in recording his 
localities. 
‘ 
A large number of the “species” described by Lea (generally 
from very insufficient material), and of those listed by Lewis, are 
synonyms. Additional species have been subsequently described by 
various authors; but also these are mostly synonyms. There is a 
rule, observed in many cases, and indicated first by Wilson & Clark, 
14, that one and the same shell assumes different shapes in the large 
rivers and in small streams and headwaters, a rule the existence of 
which will be shown‘elsewhere; and it is easily understood why the 
various local races have been regarded as good species, as long as 
