Any way to positively indentify S. nigriventis

[nonamethefish]

Is there? Im kind unsure as I've seen some that look pretty close but they don't always swim upside down. In fact, the ones swimming in panic aroudn the tank were just as often right side up as upside down. They did have the counter shading though.

Thanks!

Also, what is a good price for small fish of this species?

[Silurus]

If they have the counter-shading, chances are pretty good that they are the real nigriventris, since they are one of the very few available in the trade with this character.