Sterki: Collecting Sph.eriid.e. 479 



full of aquatic plants, estuaries, drainage-ditches, etc., are especially 

 rich in mollusks. Some of the smallest and rarest Pisidia live among 

 gravel in rivers and creeks. Tidal waters are often rich. In a small 

 tidal ditch in Mrginia large numbers of specimens of about thirty-five 

 species of mollusks were collected in less than two hours, and about a 

 dozen of them were Sphreriidae. Brackish waters should be searched 

 over carefully and may yield peculiar forms. 



Many species and forms are often found abundantly in the moun- 

 tains, even at altitudes of 10,000 to 12,000 feet above sea-level, and 

 quite a number of species have been collected within the Arctic Circle. 

 Some apparently promising places may be poor, yet yield interesting 

 forms; others are immensely rich. In some instances over twenty 

 thousand specimens of Pisidiuni alone have been taken from a single 

 locality in a short time, representing many species, some of them 

 common, others very scarce. All this shows that collecting should 

 be done thoroughly at every available place, so as to secure large 

 numbers of specimens, and all species inhabiting that place so far as 

 possible. 



Some Sphaeriidae are able to live and propagate in damp places, 

 under and between dead leaves, in muck, where water abounds only 

 in spring, or after heav}' rains; and such forms are able even to survive 

 severe droughts lasting weeks and months, as for instance Spharium 

 occidentale, usually found in company with certain aquatic snails. 

 Some Pisidia may be found among moss in damp or wet places and 

 around springs. 



It is worthy of note that difTerent regions have their peculiar forms 

 differing from each other. The molluscan fauna of the Pacific States 

 differs materially from that of the Atlantic States, and the fauna of 

 the South from that of the North. 



Collecting Outfit. 



Some of the larger mussels and snails may be found and picked 

 up singly, but in general they must be collected "wholesale." Various 

 kinds of perforated metal and wire strainers have been used, some of 

 them ingeniously constructed, but they are not satisfactory. The 

 best and the simplest thing is a net, somewhat like a butterfiy-net. 

 A piece of strong wire, 3/16 in. in diameter, and about four feet long, 

 is bent so as to form a ring of six to eight inches in diameter; the ends, 

 or shanks, are crossed over each other, and the longer end is bent 



