GLOSSARY. 105 
dorsal, belonging to the back. 
Drdpandldi, named after Drapanaud. 
Dreisséna, named after Dreissens. 
dubia, doubtful. 
edéntula, toothless. 
élegans, elegant. 
elongata, lengthened. 
epidérmis, the thin skin covering shells. 
épiphragm, a film which is secreted by the animal to cover 
the mouth of the shell. 
equilateral, having equal sides. 
ericetorum, inhabiting heaths. 
Hverétti, named after Everet. 
exalbida, whitish. 
excavatus, hollowed out. 
filament, a thread. 
flavéscens, yellowish. 
flavus, yellow. 
fluviatilis, inhabiting rivers. 
fontindle, inhabiting springs. 
foot, a flexible muscular process by means of which 
mollusks travel. 
fragilis, frail. 
filvus, tawny. 
fusca, dark brown. 
fusiform, spindle-shaped. 
