1½ pounds scallopsJuice of 6 or 7 limes or lemons2 to 3 jalapeno peppers, seeded and finely diced3 tomatoes, peeled, seeded and diced1 small red onion, finely chopped6 tablespoons chopped dill1/3 cup olive oilSalt1 avocado3 to 4 sprigs dillIf using sea scallops, slice them horizontally. (Keep bay scallops whole.) Place scallops in a rimmed dish and add enough lime or lemon juice to cover. Turn the scallops so that all sides are coated with juice. Cover the dish with plastic wrap or a plate. Marinate in the refrigerator for 3 to 4 hours. The scallops should become opaque.Drain and discard the juice from the scallops. Add jalapenos, tomatoes, onion, chopped dill and olive oil. Season with salt to taste. If not serving immediately, refrigerate until ready to serve.Peel and slice the avocado; brush the slices with lime juice to prevent discoloring. Garnish scallops with avocado and sprigs of dill.Note: As in all ceviche recipes, these scallops are "cooked" by the citrus juice. Be sure to buy only the freshest scallops and handle carefully to reduce the chances of food poisoning.Adapted from "The Classic Herb Cookbook," by Jill Norman (Dorling Kindersley, 1997).