Combine crab meat or shrimp, mayonnaise, sour cream, parsley, lemon juice and garlic salt. Slice bread in half lengthwise and arrange on baking sheet. Spread cut sides with butter. Top with cheese slices, trimmed to fit bread. Cover cheese with crab or shrimp mixture. Bake in 350-degree oven until lightly browned, about 15 minutes. Cut crosswise into serving pieces.