I have a favorite Asian supermarket in Belgrano (a mostly ritzy neighborhood in Buenos Aires). The entire back area is a crazy/busy seafood market with people buying huge plastic bags full of various sea creatures. I put my hands right next to these two shellfish so that you could see their size. giant snails on the left and something like giant steamer clams on the right, though even more creepy. I finally took the plunge and bought a couple of kilos of mejillones (mussels) and brought them home on the bus. They were very meaty, though perhaps not as tasty (if you like mussels, that is) as the Prince Edward Island variety
[you can really gross yourself out by clicking "original" below. But you will have to scroll down and to the left and click "large" again in order to return to the size you have been probably be using to view the site]
David wrote that...I do not even want to look at the photo...John