Apple Snails, or are they?

Yes, those names are usually interchangeable. The "mystery" snails I bought at petsmart were apple snails (brigs).
 
applesnails refer to a good amount of differnet species./
 
The type labeled as mystery snails are often pomacea bridgesii (commonly abbreviated "brigs").

Check out www.applesnail.net for tons of great info, as well as ways to identify the various species.
 
"Apple snail" is a blanket term usually used to refer to all species in the genus Pomacea, the same way "dog" refers to any of the species - german shepherds, beagles, boxers, mastiffs, etc.

"Mystery snail" usually refers to Pomacea Bridgesii - but it's not unusual to see other species mis-labeled this way. However, the ones you'll find at Petco or Petsmart are definitely Pomacea Bridgesii.
 
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