MOLLUSCA. 235 
fresh water, the salt remaining soon attracts moisture, which 
speedily destroys the ligaments and epidermis. 
‘The land shells are more within the reach of the scientific 
collector. To obtain these, he has only to examine the cre- 
vices of rocks, the trunks of trees, decayed wood, moss, and 
brushwood. In summer, after a shower, the land shells are 
most easily procured. The animals come forth to feed on 
the moistened blade, and at that time, from their motion, 
may be very readily perceived. 
The land shells are very easily preserved. Almost all that 
is required is the extraction of the animal. 
The fresh water shells, though less difficult to procure than 
the sea shells, require more trouble than the land shells. A 
piece of gauze spread over a ring attached to the end of a 
staff, forms a very convenient net for fishing fresh water 
shells. By means of this net in the drought of summer, al- 
most all the different species of fresh water shells may be 
obtained with ease. 
The fresh water shells are frequently covered over with 
slime or mud, which must be removed bya brush; and the 
animal may be extracted after the shell has been plunged in 
boiling water. 
Before closing our remarks on the important group of 
animals to which we have been directing the attention of 
the reader, we shall dedicate a few paragraplis to a brief 
notice respecting Fosstz SHELLS. 
Besides the shells which are found on the land and in our 
lakes, rivers and seas, and termed REcENT SHELLS, there are 
relics of many species found in our marl pits and limestone 
rocks, always somewhat altered, and which are denominated 
FosstuSuHewzs. While theshells ofthe former class have been 
eagerly sought after, few conchologists, previous to the be 
