475 
easily be accomplished by the waves of large carp and buffalo that ad- 
vance up the river every spring, and that have in recent years been 
practically confined within the bank limits of the river itself for feeding 
range until they have reached a point near or above the Lagrange dam. 
The last hypothesis as an explanation of this single circumstance, and, 
as well, of the comparative poverty of the bottom fauna of the entire 
lower 77 miles of the river, receives some support from the fact that 
while in 1915 the bottom-fauna stocks between Lagrange and Grafton 
dropped nearly to the vanishing point, both in the channel and shore 
zones, between Lagrange and Havana, where there was still a large lake- 
acreage open to the river, the important decrease in the bottom fauna 
over Havana district figures was to be seen only in the channel valua- 
tions and was apparently, for the most part, explained by the character 
of the channel bottom. 
Only two of the twelve lakes in the Havana district (Thompson and 
Quiver) were examined both in 1914 and 1915 with sufficient complete- 
ness to permit a fair comparison of their stocks of bottom animals as of 
these two years. While there was an increase of 60% in the average 
quantities (by weight) in the deeper open water of Thompson Lake from 
1914 to 1915, the changes in the shallower zones, and in both the deeper 
and shallower areas in Quiver Lake, were in the direction of decrease, 
BortomM-Fauna Stocks, Intrnors River CHANNEL, 1913 ANnp 1915, 
(JuLy—OcrToseErR) 
Average number/Average number 
individuals per| individuals per ee poeeae 
Reach collection.* sq. yard p 1915+ 
1913 1915 . 
Chillicothe to Copperas Cr. 101 203 239 
dam 10% 33 
Copperas Creek dam to 280 880 3,029 
Havana 6 16 
Havana to Lagrange 22 15 22 
2 8 16 
Lagrange to Kampsville 29 17 7 
15 i) 
Kampsville to Grafton § 28 | 6 
9 tf 
* All hauls with ordinary iron dredge, with coarser mesh bag than in 1915. : 
+ Not figured for 1913 because of less certain quantitative value of 1913-series 
of collections. 
t+ The Italic figures give the number of collections. 
§ Five hauls at the foot of Six Mile Island yielded an average of nearly 1,000 
specimens of Musculium transversum per collection; other hauls, poor. 
