Corn flour is essentially very finely milled cornmeal made from the entire kernel of corn—the germ, the bran, and the endosperm. Corn meal—whether coarsely ground, medium grind, or finely ground—is not an acceptable substitute due to the textural difference. However, masa harina, which you can find in the Latin section of most supermarkets, is a perfectly fine swap. A caution to our friends the Brits and Aussies and Canadians. We understand that in your corners of the world, “corn flour,” or rather “cornflour,” is synonymous with “cornstarch,” but that’s not what we’re talking about here. Cornstarch is ground from only the endosperm of the corn and makes a lousy coating for fried clams. Trust us.