6G60723- 176

shallow water between. A thorough collection of the shells on the surface was
made along the sand and gravel bars lining the channel and in the water across
the constricted areas as well as 2-3 feet from the shore along the entire
length. Live as well as dead unionids were picked up. 1880 shells and
shell fragments of 18 species were taken from this location at that time.

Three measurements of each shell, when possible, were taken, These
were length - measured parallel to the base line, height - measured perpendicular
to the base line, and width - measured on the outside from a plane formed
by the hinge line and the opposite edge to the deepest part of the shell.
A glass plate was propped up and gridded into 5 mm lines with éwo perpendicular
clear plastic metric scales taped onto fhe plate. The specimen was then
placed against the bottom of the glass, inner side upward, and the base line,
a line extending from the umb> to the anterior edge of a nick in the
posterior wing, common to all the specimens, was Aligned along the first
grid line. The length measurement was the longest measurement that could
be made parallel to the base line. The height was read off the grid as the

longest measurmeht between the base line and the edge of the specimen

perpendicular to the base line. Width was measured with a caliper.

RESULTS: Included are the actual measurements taken for each specimen

in the Appendix. Each parameter for a given species was summed and averaged
and is shown it)fable, along with the number of specimens for each species,

an approximation of the area of the shell (length x height) , ratio of width

to area, and minimum and maximum length measurements. Graphs 1-6 show

age distribution for the six most abundant species, (excluding Anodonta grandis
which, due to the time available, was not measured, assuming relative

length is indicative of age. Plotted are the number of shells falling

within 10 millimeter increments.