Bi-pod ID?

I noticed this shell while trying to corner a small school of yellow perch in narrow concrete canal. It's fed by a lake and has water year round. Sure enough when I started digging in the areas where the bottom is all busted up I found more. It took forever to get a decent picture at dusk but I did leave it there. I have no idea about bi-pod species so any ideas welcome.
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Looks to me like a floater (Anodonta grandis, if I remember correctly), but I'm no expert. Was the shell very thin?

Pyganodon grandis aren't on that side of the mountains, but Pyganodon cataracta is found on the Atlantic slope. That being said I would tentatively call it Pyganodon cataracta. Was the area tidally influenced? The nacre color is a little too pink for my liking. However, the umbo looks about even to above the hinge line. Without seeing the beak sculpture and feeling the shell I'm personally hesitant for a definative answer. I really need to dive into a box or two of shells and see someof the variability and diversity of Atlantic slope fauna. I was limited to a few species last year and written descriptions.

The shell was very thin and no tidal influneces. This location is a freshwater drainage/stream between two resiviors. What is the beak sculpture and what are you looking for in the texture of the shell/charaistics? You guys are great thanks!

On the beak/umbo (that part where the mussel hinges and originates from) there is sculpturing. The sculpture type differs at different taxanomic levels. It can be very helpful in identifying similar looking species. Anodonta implicata , a species similar in appearance to Pyganodon cataracta, thickens noticeable moving posterior to anterior, while the later is thin overall. They both have double looped beak sculpture though P. cataracta is a bit more rigid and can have more loops. I asked about the tidal connections versus freshwater impoundment to further help me shore up my confidence that it is not Anodonta implicata .

Very nice picture and great use of scale and background.

Someone with more power than me (I tried to move it), can we move this to the invert section?

On the beak/umbo (that part where the mussel hinges and originates from) there is sculpturing. The sculpture type differs at different taxanomic levels. It can be very helpful in identifying similar looking species. Anodonta implicata , a species similar in appearance to Pyganodon cataracta, thickens noticeable moving posterior to anterior, while the later is thin overall. They both have double looped beak sculpture though P. cataracta is a bit more rigid and can have more loops. I asked about the tidal connections versus freshwater impoundment to further help me shore up my confidence that it is not Anodonta implicata .

Very nice picture and great use of scale and background.

Someone with more power than me (I tried to move it), can we move this to the invert section?

Thank you. Now I'll remember to take a beak photo next time. I'm a complete amatuer/non educated hobbist. Any tips I get from you tech guys are important to learning. I started carrying a 24"x24" back rubber mat and the green scale pad I picked up at the craft store for pics. Thanks Again.

http://forum.nanfa.o...?showtopic=3321

I know absolutely nothing about mussels so you'll have to "google" those terms.