This Paella--Arroz de almejas a la marinera--comes from Penelope Casas who says that in Valencia, paellas tend to be either meat or seafood -- and not both. This delicious paella owes its intense clam flavor to its use of two kinds of clams. The larger ones are steamed open, then the meat chopped and the broth used as the paella's liquid. The smaller ones are placed in their shells directly on the paella to steam open while the dish cooks. To cleanse clams, place them in a bowl and cover them with heavily salted water (think seawater) and a tablespoon of cornmeal or flour. Leave for a few hours or overnight. Before using, scrub them well.