They're Elimia comalensis.  Normally found in springs and rivers on and along
the Edwards Plateau.  They are commonly smooth, but some do have the
striations.

Russ Minton
University of Louisiana at Monroe

Quoting David Kirsh <[log in to unmask]>:

> Anyone willing to take a look at a couple of fresh water snails I
> found in Texas? The image and particulars are to be found at the
> Let's Talk Seashells forum.
>
> Try:
> http://s14.invisionfree.com/Conchologist_Forum/index.php?showtopic=76&st=0&#entry1417438
>
> Or try: http://s14.invisionfree.com/Conchologist_Forum/index.php?act=idx
>
> Thanks,
>
> David
>
> Man's attitude toward nature is today critically important simply
> because we have now acquired a fateful power to alter and destroy
> nature. - Rachel Carson, early 1960s
>
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