80 MOLLUSCA, CRUSTACEA AND REPTILIA FOR 



The genus Paludlna is also a helical shell, but more 

 conical than the last genus, and bears a little resemblance 

 to a stout Lymnca. There are ouly three species fouutl 

 in our State ; but I have some in my tank that came 

 from the Delaware River, which are slow animals, but from 

 being large and light in color, they form a good contrast 

 to the Lymnca and Planorbi. 



Paludlna decisd (PI. V., Fig. 2) is the commonest of 

 the New York species. 



The shells of the genus Melania form a good contrast 

 in appearance to the other fresh-water shells, being elon- 

 gated cones. They are, however, unfortunately mostly con- 

 fined to the Southern and Western States, and are not 

 found m Europe except in fossil state. They are slow 

 creatures in their motions, but are good grazers. 



Of the bivalve shells we have the genus Unlo, or fresh- 

 water mussel, as it is called, which may be introduced into 

 our Aquarium. There are quantities of species of this 

 genus in this country, and. many of them are very com- 

 mon, as U. complanatns and If. radiatus. There are twelve 

 other species found in this State. They are not, however, 

 lively creatures, and are of no use in cleaning the glass. 



There are ten species of the genus Anodan found in this 

 State (of New York), one of which, A. jlmiatllis, is very 

 common. 



The Crustacea next demand our attention, and are also 

 fair scavengers, and more lively in the performance of 

 their duties than their fellow-workmen, the Molluscs. They 

 do not, however, dean the glass, but only sift, as it were, 

 the decomposing matter out of the water. Yet even if 



