ok so this may sound like a stupid question. But is it illegal to sell certain moniters in pet stores?

Cause i cant believe what i saw today. I think it was a moniter of some kind..and it was MASSIVE. Probably about the size of my 50lb dog and of course very long..
The cage didnt say what it was either..which made me kinda suspicious. Not to mention the fact that it was going nuts in the "cage" and then there was a sign that said for serious buyers only..as far as them taking it out of the cage. I wish i had taken a picture because it was unbelievable. Does that sound like some kind of moniter?