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, spring onions and garlic until tender. Stir in prawns, scallops and crabmeat. Cook for 5 minutes, or until prawns are pink. Stir in wine, lemon juice and butter; cook until heated through.