REPORT ON THE STUDY AND APPRAISAL, ETC. 9 
were obtained from the water weed, to which they were at- 
tached by their byssus thread. The dredge had the disadvan- 
tage of being apt to foul on some obstruction, and was be- 
sides very unwieldy, being apt to hinder the progress of the 
work. Juveniles taken were at once preserved in a mixture 
of 4 per cent formalin, 70 per cent alcohol and shell dust, the 
latter substance preventing erosion of the shell by the other 
chemicals. They were labelled, counted, and shipped to the 
Fairport Biological Station. The number obtained at each 
locality is expressed in parenthesis after the number of ma- 
ture mussels obtained there; upon the sum of the two at any 
locality all calculations are made. Other biological specimens 
were at early opportunity shipped to the various specialists 
for identification, and the results of their work, which is here- 
by gratefully acknowledged, is comprised in the notes on the 
various areas. 
(c). Determination of localities. 
The course of the river was followed by means of a set of 
maps of the river published by the Mississippi River Com- 
mission, and by a copy of the current edition of the light list 
for the 13th Lighthouse District as in use by navigators on 
the river. The position of each locality surveyed is indicated © 
on the maps used, which are now in possession of the U. S. 
Biological Station, Fairport, Iowa. On these maps, the lo- 
calities are numbered according to area, and to the order in 
which they were examined. Thus 1-3 on the map indicates 
Area 1 and the third locality in it. Reference to the data to 
follow are to be similarly understood. As previously indi- 
cated, only the three best localities in each Area are reported 
upon. 
It was not found practicable to draw into the maps these 
localities on an exact scale. The markings largely indicate 
the relative position of the locality with regard to the 
shore line at the time, the more absolute one being obtained 
by reference to the descriptive material given in connection 
with the markings on the maps. The more absolute data con- 
cerning the position of the locality was obtained by reference 
to some object or formation along the shore which seemed of 
a fairly permanent nature, such as the Government Lights or 
