
area 1) days after treatment. Samplings in the check area revealed little 
change throughout this period. 
Ribbed iiussel, Volsella demissa 

This is probably the commonest mussel along the Hast Coast. It 
is characteristic of the intertidal zone where it occurs embedded in the 
marsh sod or in comparatively firm mud banks of ditches and creeks, as well 
as on pilings and other objects in the water. 
Information cn populations of this mussel was derived primarily 
from soil-surface samplings. However, a foot-square sample proved inade- 
quate for statistical purposes. Counts from all areas before spraying 
averaged only 2.8 mussels per sample and varied from 0.4 to 7.0, the. 
variation being due largely to the colonial habit of this animal. Some 
individuals may have been overlooked by reason of their protective colora- 
tion and limited projection above the soil surface. It appeared that DpT 
treatments had little effect on mussels, since the average number of live 
incividuals in samplings on all areas after the second spray was 3.1], an 
average increase of 0.3 mussel per sample. 
Saltmarsh Snail, Melampus lineatus 
This is the commonest snail in the saltmarsh habitat. Its 
greatest abundance occurs in the sod and grass at the upper levels of the 
tidal range. Black ducks use it as food--sometimes in quantity. It is 
eaten by the clapper rail to a lesser extent. 
Soil-surface sampling was the principal method used in deter- 
Mining the effects of DDT spraying on these snails since general observa-~ 
tions revealed no noticeable population differences. As a rule, there was 
an increase in the number of live snails per foot-square sample in all 
areas after spraying. A few decreases were noted on several of the treated 
areas, principally in samplings made after the second spray application, 
The check area showed an increase at this time. Volumetric measures of 
all collections gave figures that corresponded closely to the increases 
in numbers. Furthermore, calculations of the averaze size of an individual 
snail at the time of each sampling revealed a progressive increase in ali 
but the 1.6 area as the season advanced. This highest dosage plot showed 
a general decrease in average snail size due to large increases in numbers 
of small snails. 
22 
