CONCHOLOGIA CESTRICA. 25 
or strings. The young appear in twenty days, or more, 
being influenced very much by moisture, and tempera- 
ture; and are provided, at first, with a shell of about 
one and a half turns. Unable to subsist without moist- 
ure, the snails inhabit damp, and secluded, places, under 
stones, logs, and fallen leaves; often in pastures, lawns, 
and gardens. Unlike the slugs, they hibernate during 
winter, either in their summer retreats, or buried deeper 
in the earth. On the first occurrence of frost, they retire 
to their mural homes, close the aperture of the shell, 
with a thin transparent membrane, ¢he epiphragm,; and 
as the animal retreats, still farther, other epiphragms 
are successively formed. 
DIAGRAM OF THE SUB-FAMILIES, SUB-GENERA, AND SPECIES, OF 
THE FAMILY HELICID/A. 
FaMILy. Sus-FaMILIEs. SuB-GENERA. SPECIES. 
albolabris, 
Sayil, 
Pennsylvanica, 
Mesopon. clausa, 
thyroides, 
bucculenta, 
*« var. rufa, 
dentifera, 
HELICIN. palliata. 
appressa, 
tridentata, 
, fallax, 
Trroporsis. introferens, 
** var. minor, 
inflecta. 
monodon, 
STENOTREMA. { Hirsute. 
_ ANGUISPIRA. alternata. 
HELICID#. Macrocyctis. concava. 
[ fuliginosus, 
laevigatus, 
inornatus, 
sub-planus, 
ZONITES. ligerus, 
demissus, 
gularis, 
HELICELLIN. suppressus, 
internus. 
cellaria, 
H indentata, 
YALINA. electrina, 
arborea, 
hydrophila. 
PSEUDOHYALINA. minuscula. 
VALLONIA. minuta. 
PATULA. striatella. 
VALLONINE. STROBILA. labyrinthica. 
HELICcOoDISCcUS. lineatus. 
PUNCTIN. PuNcTUM. minutissimum. 
