300 American Geologist. ^^y- ^^^^ 
Johnson says : "The land tribes seem to refuse no tender herb ;" 
. and in another place : 
"On occasions they eat voraciously ; but, when necessary, they can 
sustain a fast longer, perhaps, than any other animated beings : snails 
having been kept for upwards of a year, nay, for years, and the Lim- 
naeae and Planorbis for many months, without any food, except that 
small and tenuous portion which they might extract from the air and 
•water." 
The same authlor referring to heVbiverous mollusks occa- 
sionally zoophagous, says : 
"The pulmonated gasteropods have a strange hankering after flesh, 
and become very cannibals in satisfying this propensity. Lister asserts 
that snails will eat fiesh of all kinds, particularly fish and salted meat; 
and that having once placed an individual of the Helix aspersa with 
another of the Arion ater in a vessel together, he found on the follow- 
ing day, that the former had slain the slug, and had miserably torn and 
€aten its skin." 
And also that — "In the absence of other nourishment, they will even 
devour each other, piercing the shell near its apex, and eating away the 
upper folds of its inhabitant. This accounts for the mutilated and often 
imperfectly repaired state of the upper volutions of some specimens." 
So it would seem that under whatever conditions and tem- 
porary changes the loess snails existed their wants were suffic- 
iently provided for, if the one condition of aridity be excluded. 
Even that can be endured in a torpid state in climates where 
the alternating rainy season affords ample opportunity for 
propagation and development ; but if they passed half the year 
in hibernation on account of cold, and the other half in the 
torpor demanded by aridity, even such prolific creatures as 
snails must have shown a steady decrease as the bluffs grew in 
hight instead of the very marked increase that the hill-tops 
proclaim. 
