HABITS AND FACULTIES. 11 



been introduced retain their native habits. Tachia kortensis, for instance, 

 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 we have the yellowish-green, 

 xinicolored variety, once described as Helix subglobosa ; and on another, 

 within a very short distance, we find a banded variety, and none others. 



In regard to colors, our snails are quite plain and exceedingly uni- 

 form ; in this respect, also, differing essentially from the species of the 

 Old World. They vary from yellowish-green through horn-color to chest- 

 nut, most of them being simply horn-colored. This is perhaps owing to 

 the fact that our species do not infest our gardens and open fields, but 

 are generally confined to forests, sheltered under logs and stones, and 

 are rarely seen abroad except during twilight or on damp and ^lark 

 days ; indeed, they almost entirely disappear as the forests are cut 

 down, and seem to flee the approach of man. The European species, on 

 the other hand, follow in the track of cultivation, and are common in 

 gardens and fields, on walls and hedges, and other places exposed to the 

 action of light. With the exception of Patula alternata and Hemi- 

 trochus varians, Liguas fasciatus, etc., there is scarcely a species having 

 bands or variegated colors inhabiting eastern North America ; and even 

 these latter species can scarcely be regarded as an exception, as they 

 are only to be found at the southern part of Florida, and are more 

 properly West India shells. In Texas, and beyond the Sierra Nevada 

 and Cascade Mountains in Oregon and California, many of the species 

 have one or more bands. 



Another peculiarity of the American snails is the toothlike appen- 

 dages with which the aperture of a large proportion of them is armed, 

 and which are characteristic of the group designated by Ferussac under 

 the name Helicodonta. More than one half of the whole number, and 

 more than three fourths of those with reflected peristome, are thus pro- 

 vided. In some species these appendages assume the form of folds 

 rather than teeth ; and in others we have simple threads or laminae 

 revolving within the aperture in the course of the spire. They are not 

 formed until the shell has attained its full growth. 



The genera not furnished with an external shell are more especially 

 nocturnal than the other families of the order, and they are so rarely 



