SHELLS

(Class: Gastropoda)

## Family: HYDROBIIDAE ##

Tolerance Value : 8

3-7 mm high

opening on the right

inflated whorls

mark on operculum (‘lid’ at the opening) is a single continuous line (spiral)

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## Family: VIVIPARIDAE ##

Tolerance Value : 6

20-60 mm high

opening on right

inflated whorls

mark on operculum has series of oval lines successively smaller inside each other (like tree rings)

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Family: LYMNAEIDAE ##

Tolerance Value : 6

5-50 mm high

opening on right

no operculum

elongated

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## Family: PHYSIDAE ##

Tolerance Value : 10

5-20 mm high

opening on left

no operculum

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## Family: PLANORBIDAE ##

Tolerance Value : 7

coiled, flat shell

no operculum

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(Class: Bivalvia)

## Family: SPHAERIIDAE ##

Tolerance Value : 8

“pea clams”

2-10 mm long

thin and fragile

color of shell – whitish/cream/light tan/gray

growth rings are close together, shell is hardly raised

feels smooth

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## Family: CORBICULIDAE ##

Tolerance Value : 8

“Asian Clams”

35-50 mm long

thick and strong

color of shell – blackish/green/brown

growth rings far apart and raised in successive ridges

feels rough