INDEX. 23d 
Fresh-water limpets, 205. 
mussels, 25 ; extinct species of, ib. 
G. 
GANGLIA, 17. 
Gasteropoda, structure and physiology of the, 44; shell of, 
ab.; animal of, 46; digestive organs of, 48; lingual 
ribbon of, 7b. ; respiration of, 52; nervous system of, 
ab. ; reproduction of, 7b. ; food of, 53; habits of, 2. 
Gasteropodous animals, 3. 
Geological distribution of, the Unionide, 25; Helix, 145 ; 
Bulimus, 147 ; Pupa, 153 ; Clausilia, 166 ; Carychium, 
178 ; Limnza, 186 ; Physa, 202; Ancylus, 206 ; Pla- 
norbis, 211. 
Geomalacus maculosus, 83. 
Glochidium, embryonic form of Anodon, 18. 
Growth of, operculum, 46 ; of shells of land snails, 95. 
H, 
Heap of Gasteropods, 47. ° 
Helicella, characters of the genus, 103 ; species of, 10-4. 
alliaria, 106. 
cellacia, 105 ; teeth of, ab. ; jaw of, 104. 
erystallina, 108. 
excavata, 108. 
fulva, 110. 
nitida, 110. 
nitidula, 107. 
pura, 107. 
radiatula, 109. 
Helicidz. See Land Snails. 
Helicine, 115. 
Helix, synoptical list of species of, 111; geological distribu- 
tion of, 145. 
aculeata, 133. 
arbustorum, 137. 
Peseere 
