LAND AND FRESH-WATER SHELLS. 413 

- being taken not to fracture fragile shells, or break the brittle 
margins of univalves by too violent shaking. Shells that 
__ adhere to flat smooth rocks may be taken expeditiously with 
the net. 
d To take Uniones, the collector will succeed best in shallow 
= water by wading. Long rubber boots are desirable for this 
= work; also, a pair of metallic 
_ tongs (Fig. 3), the handle of 
_ one blade lengthened by a 
_ wooden rod, to be held by one 
hand to direct the instrument 
in its work, while the other ™ 
hand pulls a cord that causes the other blade to close on the 
_ Specimens to be taken. A basket carried on the arm serves 
_ to hold the specimens, which should be handled carefully. 
= An iron garden rake may sometimes be used with much 
i advantage to uncover species where the current will wash 
Way the turbid water. When the water is cleared, the 
shells may be seen and can be picked up by means of the 
ss, net, or dipper, or even with the rake, if not too 
Small. In lakes and ponds, where the bottom is muddy and 
@®Uniones can be seen from a boat, the dipper, used so as 
_ hot to make the water turbid, will answer the purpose. If 
the bottom is gravel the tongs may be used. In deep dark 
Water in rivers, Uniones are sometimes drawn ashore in 
seines used for fishing. They have also been secured by 
Means of rakes. 
It often happens that there are small mollusks that feed on 
Aquatic plants, and can seldom be found elsewhere. This is 
the “ise in lakes and in rivers that have only a moderate 
current, Such species will seldom be obtained with either 
het or dipper, and the collector will be obliged to content 
himself with slower processes. By carefully lifting the 
«Weeds out of the water the little mollusks may be found on 
oe es and leaves. They very usually detach themselves 
n disturbed, but if they are once fairly above the water, 

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