Freshwater Molluscan Fauna 
111 
Table 2. Species of freshwater mollusks collected from Greenfield Lake with 
collection stations. 
Species 
Collection stations 
Gastropoda 
Viviparidae 
Campeloma decisum (Say, 1817) 
Lymnaeidae 
12, 
13, 
15 
Pseudo sue cinea columella (Say, 1817) 
Physidae 
9, 
11, 
16, 
17, 
18 
Phy sella hendersoni (Clench, 1925) 
3, 
4, 
6, 
8, 
11, 
18 
Phy sella heterostropha (Conrad, 1834) 
Planorbidae 
4, 
7, 
8, 
10, 
11, 
16, 18 
Gyraulus deflectus (Say , 1824) 
6, 
8, 
10 
Gyraulus parvus { Say, 1817) 
16 
Menetus dilitatus (Gould, 1841) 
7, 
10 
Planorbella trivolvis (Say, 1817) 
4, 
5, 
12 
Helisoma anceps (Menke, 1830) 
Ancylidae 
6, 
8, 
17 
Ferrissia fragilis (Tryon, 1863) 
3, 
7, 
8, 
10, 
11, 
14 
Bivalvia 
Mactridae 
Rangia cuneata (Gray, in Sowerby 1831) 
Cyrenidae 
1 
Polymesoda caroliniana (Bose, 1802) 
Unionidae 
1 
Anodonta cataracta (Say, 1817) 
2, 
7, 
10, 
12, 
13 
Anodonta imbecillus (Say, 1829) 
Sphaeriidae 
13 
Musculium transversum (Say, 1829) 
5, 
15 
Sphaerium occidentale { Prime, 1853) 
4 
Sphaeriid clams were numerically the most abundant bivalve mollusks 
in the lake system. High densities of Sphaerium occidentale and Musculium 
transversum were discovered under algal mats in nearshore areas during 
the January 1984 drawdown, but numbers were much reduced in the 
summer of 1987. 
Only Rangia cuneata (Gray, in Sowerby 1831) and Polymesoda 
caroliniana (Bose, 1802), both brackish-water species, occur in the creek 
below the spillway. Salinity appears to be the limiting factor for 
freshwater species in this area as tides bring brackish water from the 
Cape Fear River into the creek. Surface salinity measurements taken 
