INDEX. 
235 
Fresh-water limpets, 205. 
- mussels, 25 ; extinct species of, ib. 
G. 
Ganglia, 17. 
Gasteropoda, structure and physiology of the, 44; shell of, 
ib. ; animal of, 46 ; digestive organs of, 48; lingual 
ribbon of, ib. ; respiration of, 52 ; nervous system of, 
ib. ; reproduction of, ib. ; food of, 53 ; habits of, ib. 
Gasteropodous animals, 3. 
Geological distribution of, the Unionidse, 25 ; Helix, 145 ; 
Bulimus, 147 ; Pupa, 153 ; Clausilia, 166 ; Carychium, 
178 ; Limnaea, 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. 
Head of Gasteropods, 47. 
Helicella, characters of the genus, 103 ; species of, 104. 
- alliaria, 106. 
—— cellaria, 105 ; teeth of, ib. ; jaw of, 104. 
--- crystallina, 108. 
- excavata, 108. 
- fulva, 110. 
- nitida, 110. 
- nitidula, 107. 
- pura, 107. 
- radiatula, 109. 
Helicidae. See Land Snails. 
Helicine, 115. 
Helix, synoptical list of species of, 111; geological distribu¬ 
tion of, 145. 
-- aculeata, 133. 
- arbustorum, 137. 
