Congratz! That's quite a find. It's probably N. x. ventrata, though, which is a hybrid of N. alata and N. ventricosa. There's a nursery that distributes plants as "N. Alata" (notice the improper capitalization of the species epithet) because they name their hybrids after the seed parent, which has caused some confusion as you can probably imagine. Still, a very nice plant; very sturdy and robust, a perfect subject to learn about the genus.
Best luck,
~Joe
PS - Darn you Clint, stealing my thunder.