110 
William F. Adams 
Salinity measurements in the creek below the dam were taken 
during and after the 1986 drawdown. All measurements were taken 
from surface waters and determined by using a refractometer. 
Identifications of Unionidae were made using Johnson (1970). 
Sphaeriidae were determined from Herrington (1962) and Burch (1975), 
and the nomenclature follows Burch (1975). Gastropods, excepting the 
Ancylidae, were identified using Burch (1982), and his nomenclature is 
used. Identification and nomenclature of the Ancylidae follow Basch 
(1963). 
RESULTS 
Sixteen species of mollusks, 10 gastropods and 6 bivalves, were 
collected from Greenfield Lake, its tributaries, and the creek below the 
spillway (Table 2). Twelve species were recorded from the lake or the 
drainage basin for the first time, and 15 species previously reported were 
not relocated. 
Campeloma decisum occurred in only one tributary. Planorbella 
trivolvis and Helisoma anceps were relatively common throughout the 
lake in the nearshore area. Pseudosuccinea columella was found in quiet 
waters of the finger portions of the lake but was absent from the main 
body of the lake. Because of the fragility of the shell of P. columella , 
occasional waves may render the main body of the lake unsuitable 
habitat for that species. Menetus dilatatus and Gyraulus deflectus were 
common in the upper end of the lake. Gyraulus parvus was found only 
in the golf course ponds of Station 16. Ferrissia fragilis was common 
on leaf litter and trash throughout the lake. 
Anodonta is the only unionid genus now occurring in the basin. 
Anodonta species are normally associated with lentic habitats, and all 
live specimens were obtained from the upper portions of the lake. 
Anodonta cataracta may be common in the central portions of the lake; 
numerous valves of this species were found at the interior base of the 
dam during the drawdown period. Three forms of A. cataracta occur in 
the lake: a form with dorsal and ventral margins roughly parallel, a 
form with a broadly rounded ventral margin, and a form with a concave 
ventral margin. 
Only one valve of Andonta imbecillus was found during the present 
study, in the fall of 1987 on a spoil pile resulting from rechannelization 
of the tributary at Station 13. Despite extensive searches of other spoil 
piles, no additional specimens could be located, and none were found 
during drawdowns. Because this tributary was at least temporarily 
disrupted, the status of A. imbecillus cannot be determined. It is at best 
extremely rare, and perhaps it is extirpated from the Greenfield Lake 
basin. 
