Hi Eric,
Traditionally, Stomatolina danblumi would probably have been lumped under the name Stomatella papyracea. It may very well be that "Stomatella" papyracea should be moved to the genus Stomatolina, as the generic names are in a constant state of flux. However, someone had some pretty good evidence that S. danblumi looked to be a separate species or they probably wouldn't have named it. I agree that your shells look very much like that species, and there are a couple others that have almost exactly the shape and sculpture of your snails (at least the one in the photo that shows the sculpture so clearly). Color can be a very poor identifying characteristic in this family, and particularly in this subfamily, with shells in the same populations ranging from black to white and with red, yellow, green, and brown variants, and they may be solid colored, "flamed" or blotched, or striped! All the Stomatella species have comparatively large animals, but most aren't as out of proportion as S. varia, S. impertusa, or S. planata. It will be really interesting to see what your snails look like in a few months. Keep us posted.
Cheers,
Don