THE 
AMERICAN NATURALIST. 
VoL. x.— JUNE, 1876. — No. ¢. 
IO AND ITS HABITS. 
BY DR. JAMES LEWIS. 
R a mountainous region comprising adjoining portions of the 
States of Virginia, North Carolina, Tennessee, and Kentucky 
arise numerous small streams which unite to form the principal 
rivers which are the head-waters of the Tennessee River. All 
these streams, not excepting the upper portions of the Tennessee 
River itself, have in a greater or less degree the characters of 
mountain torrents, which in reality they seem to be on a very 
grand scale. The streams have very usually a rapid descent, and 
are in many places broken by shoals and rapids, the beds of the 
Streams being usually coarse gravel or rock ; there are seldom to be 
found stretches of placid water, and accordingly, as might well be 
conjectured, the fauna of the region, so far at least as relates to 
tesh-water mollusks, is somewhat peculiar. In the gravelly por- 
tions of some of the streams abound numerous species of Unio; on 
ts and shoals are found immense numbers of operculate univalve 
mollusks, and in the rapids, especially in rocky portions of the 
Principal rivers, are found the beautiful and interesting shells of 
Species of Io, which are the largest and most attractive univalves 
of the family to which they belong. The earliest account we have 
of this group of shells may be found in the Journal of the Academy 
of Natural Sciences, November, 1825, in which Mr. Say described 
* Species: found in the North Fork of the Holston River in Vir- 
ginia, calling it Fusus Jluvialis. From that time until quite re- 
cently, additional species have from time to time been published, 
all of them being referred to the Holston River or more vaguely 
to “ Tennessee,” Even so late as 1873, there was only a single 
record Showing that Io had been found in any stream other than 
the Holston River. The record here alluded to occurs in the 
merican Journal of Conchology, vi. 223, and bears date October 
gg 
Copyright, A. S. PACKARD, JR. 1876. 
