Comparisons with other Prosobranchs
All local prosobranchs are dextral snails with a fairly solid to very solid shell and an operculum.
Note that the operculum is lost from dead shell and can be withdrawn beyond view in preserved shells.
| nzms | Valvata |
 |
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Some species are widespread and abundant in streams, rivers and lakes.
They often occur with the nzms.
These snails are greatly depressed compared to the nzms and they have a nearly circular aperture.
| nzms | Bithynia |
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The single species here, Bithynia tentaculata Linnaeus is introduced from Europe.
It occupies scattered lakes and ponds across Montana and probably elsewhere also.
It is sometimes very abundant. It has not been seen together with the nzms.
This species is more like 10 mm tall and much broader than the nzms.
It also has a thick, calcareous operculum with concentric growth lines.
| nzms | Melanoides |
|
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The single species here, Melanoides tuberculatus (Muller) is introduced from Asia or Africa.
This common aquarium species has been introduced into scattered warm springs across the west.
It always occurs with tropical fish.
It does not escape into more normal waters, except in the extreme southern USA.
This species has not been seen together with the nzms.
It is much larger (15-40 mm), more solid, more tapered and has more whorls than the nzms.
It is also has a sculptured shell with some color patterns normally present.
Like the nzms, it is an all-female, parthenogenic live bearer.
2002 JUNE 18, last updated on 2005 FEB 05
