Cook pasta shells according to package directions. Drain.
Pour half of sauce into 8x10 baking dish. Combine spinach, ricotta, 3/4 cup mozzarella, Parmesan, and egg. Mix well. Fill each shell with mixture and place in dish. Top with remaining sauce, cover, and bake at 350 degrees for 45 minutes. Sprinkle with remaining mozzarella before serving.
