THE NATURAL HISTORY SURVEY. 139 
over the aperture. The formation of this membrane (epi- 
phragm) is as follows: ‘‘The animal being withdrawn into the 
shell, the collar is brought to a level with the aperture, and a 
quantity of mucus is poured out from it and covers it. A small 
quantity of air is then emitted from the respiratory foramen, 
which detaches the mucus from the surface of the collar, and 
projects it in a convex form, like a bubble. At the same mo- 
ment, the animal retreats farther into the shell, leaving a vacuum 
between itself and the membrane, which is consequently pressed 
back by the external air to a level with the aperture, or even 
farther, so as to form a concave surface, where, having become 
desiccated and hard, it remains fixed. These operations are 
nearly simultaneous and occupy but aninstant. Asthe weather 
becomes colder the animal retires farther into the shell and 
makes another septum, and so on, until there are sometimes as 
many as six of these partitions.’”* 
During hibernation the heart almost ceases to beat, and all 
the functions of the body cease, the animal becoming torpid, 
to be awakened only when the warm days of April or May ap- 
proach. Thereason for hibernation is seemingly only to enable 
the organism to withstand the cold climate, and to exist during 
a period when the food supply is cut off. When kept in con- 
finement they do not generally hibernate, but live during the 
winter as in the summer. 3 
The comparative speed of snails while in motion does not 
seem to have been studied to any great extent. Asa matter 
of curiosity the writer timed a few species, with the result as 
tabulated below: 
EVITA PALI ELTS hy clk ada a4 Diets Pym: diole a8 2inchesin 45 seconds. 
“s PADELACA a ctarite yes tance: oe biti, atlas a Drives or) oy 
bd GUDEDSISeer desc aa ips w9k Gig sels e0 7. le tre 30, me 
a RRR Ny Paechian hana nce ok 2g aActs, 1 hase BW nt ois 3) Z 
PY DELCTOREFODA iin ceibip ns poe ee ee ae Sse Siezao s 
WAWI DATs COMLCCLOIGES iii 05 «04 0/00 0's bee woe ite Pe ** 120 a 
OCR) PORE FIN h. oes s oe ene werelcale al sail) x 
‘ ERACEMAIDET ate Gis, 3 Sig hs Oia ky pw i aus 60 s 
¥ BONO 8 la Ala har geese oo ar aenn? “ 120 u 
oe GIOPMONURES Vcd 5 ROS so ie yoo w' bach aw 0M ota “ 60 ig 
SECU ATIA CONCAVA 6 cotnt lect ina des verdes Ce e090 iy 
SUBORDER STYLOMMATOPHORA 
Tentacles four in number, the superior retractile, with eyes 
*W. G. Binney, ‘‘A Manual of American Land Shells, p. 10-11.’’ Bull, U. S. Nat. 
Museum, No. 28, 1885. 
