Bring a large pot of lightly salted water to boil, add pasta shells, and cook for 8 to 10 minutes, or until al dente; drain.
Heat olive oil in a large pot over medium heat.
Saute mushrooms, green onions, and garlic until tender. Stir in shrimp, scallops, and crabmeat. Cook for 5 minutes, or until shrimp is pink. Stir in wine, lemon juice, and butter; cook until heated through.