Shellfish Watermelon Ceviche

Name: Shellfish Watermelon Ceviche
Ingredients: 1 navel orange; 1/2 cup plus 2 tablespoons fresh orange juice; 1/4 cup fresh lime juice; 1/2 cup diced (1/4 inch) seeded watermelon; 1/2 teaspoon finely grated peeled fresh ginger; 1 1/2 tablespoons finely diced red onion; 2 to 3 teaspoons finely chopped fresh jalapeño chile; 1/2 teaspoon salt; 1/4 lb sea scallops, tough muscle removed from side of each if necessary and scallops cut into 1/2-inch pieces; 1/4 lb large shrimp in shell (21 to 25 per lb), peeled, deveined, and cut into 1/2-inch pieces; 1/4 lb cooked lobster meat, cut into 1/2-inch pieces; 1 1/2 tablespoons chopped fresh mint; 4 heads Bibb or 2 heads Boston lettuce (1 1/4 lb)