12 A MANUAL OF AMERICAN LAND SHELLS. 



from their lurking places while the sun shines, and indeed are never 

 seen ranging in the daytime unless the day be damp and dark. Should 

 they then be surprised by the appearance of the sun, they immediately 

 take shelter from its rays under some cover or on the shaded side of 

 the trunks of trees. 



Their natural food is vegetable, and the formation of the mouth and 

 the organs with which it is armed seems to be peculiarly well adapted 

 for cutting fruits and the succulent leaves of plants. The cutting-edge 

 of the jaw being applied against the substance to be eaten, the semi- 

 lunar rough instrument, which Spallanzani calls the tongue^* is brought 

 up against it, cutting out and carrying into the mouth semicircular 

 portions of nutriment. This operation is carried on with great rapidity, 

 and the substance to be eaten soon disappears. It is certain, however, 

 that some species are also fond of animal food, and sometimes prey 

 upon earth-worms, their own eggs, and even upon each other; but the 

 slowness of their motions and their consequent inability to pursue prey, 

 forbids the idea of their being dependent on animal food. They, in 

 their turn, become the prey of various birds and reptiles; and it is no 

 uncommon thing to observe, in the forest, clusters of broken shells 

 lying ou logs or stones which have been chosen by birds as convenient 

 places for breaking the shell and extracting the animal. 



The snails of the United States are for the most part solitary in their 

 habits, differing very much, in this respect, from the snails of Europe. 

 It is true that in localities favorable for their residence they may be col- 

 lected in considerable numbers; and especially is this the case in the 

 States north of the Ohio River. But even there they seem to live inde- 

 pendently of each other, and not to unite into herds or communities. 

 There are occasional exceptions, however, as in the case of Patula alter- 

 nata, very large numbers of which ha7e been observed collected into a 

 small space, especially in winter, as if for the puri)ose of imparting 

 warmth to each other. The few species of European snails which have 

 been introduced retain their native habits. Tachea hortejisis, for in- 

 stance, which has been transplanted to some of the small islands in 

 the vicinity of Cape Ann, is found there in countless numbers, literally 

 covering the soil and shrubs. It is worthy of notice also that each 

 island is inhabited by a variety peculiar to itself, showing that the 

 variety which happened to be introduced there has propagated itself, 

 without a tendency to run into other variations. Thus, on one islet is 



* This organ is called the " lingual membrane " in the text. By others it is called 

 the "radula." . 



