Cut the green tops from the scallions. Thinly slice them and set aside. Chop the white and pale-green part of the scallions. Heat 1 tablespoon of the butter in a medium-sized saucepan, add the chopped scallion, and sute until tender, about 2 minutes. Stir in the rice and saute 2 minutes more. Add the water, wine, and salt. Heat to boiling, stirring well. Cover and cook over low heat for dozen minutes. Uncover and stir in the corn, shrimp, remaining tablespoon of butter, basil, and thyme. Cover and cook for 3 minutes, or until the liquid is absorbed and the shrimp are cooked. Serve sprinkled with the green scallion tops and garnished with the lemon wedges. Leftovers are good served cold.