MONOGRAPH OF THE GENUS STROPHIA. 
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i 
drawn inward by a muscle attached near the termination on the inside, 
as is usual with members of this family. For further special anatom- 
ical structure see Specific Characters under head of individual species, 
and in General Conclusions. 
GENERAL HABITS. 
All of the species of Strophia that I have seen living are gregari- 
ous, hundreds often occurring within a few square inches, frequently 
clinging together, one top of the other, sometimes three or four deep. 
When thus found, they are hybernating, or if in the tropics, passing the 
dry season in a state of inactivity, and as a rule, whenever rain falls, 
even although it be for a short period, they immediately begin to move. 
They are herbivorous, and even when inactive, remain upon the plants 
or shrubs on which they feed, or near them, rarely retreating beneath 
stones. 
It is probable that the eggs are laid upon the branches of shrubs, 
or other similar situations, although at present I can state nothing def- 
inite regarding their breeding habits. I have never seen any very young 
shells of this genus, the smallest consisting of four or five whirls. 
When an animal of Strophia wishes to retreat within its shell for 
any purpose, it withdraws itself well within the aperture, by this act, 
partly doubling the foot; from this doubled foot and. the mouth, exude a 
clear, thick, glairy fluid that soon hardens when exposed to the air. By 
muscular contractions, the foot or surface of it, that comes in contact 
with the now hardening film, is undulated, thus separating it from the 
completely hardened and transparent wall. The foot is now withdrawn, 
then follows the remainder of the body, the ventral orifice, Plate 1, fig. 6 
Y, being the last to be taken away. This occupies the lower right hand 
corner of the aperture and leaves a small hole. The animal now dis- 
appears, retreating as far back as the third whirl, but at about .25 from 
its final resting place, a second partition, ( Plate H, 1, c, where the white 
partition may be seen in the second whirl, ) is formed; the first wall is 
straight and, as remarked, transparent; the second is curved downward 
on the outer side and is nearly as opaque as rice paper which it resem- 
bles. Both walls are readily soluble in water, so that these would form no 
protection in case the animal fell into the water, for being air breathing, it 
would soon perish. The time occupied in constructing the first wall, is 
about three minutes. Occasionally a third wall is constructed, it being 
the object, evidently, of the animal to retreat within the shell as far as 
possible, where it remains when alarmed or during the period of hyber- 
nation. 
