Arselle are tiny clams that live in the swash zone, and when I was a boy in the 60s, men with their pants legs rolled up would gather them by dragging a large strainer contraption through the sand of the shallows. Alas, like many other sea animals they've been overharvested and are nowhere near as common as they once were. In the absence of live arselle you'll want small live clams to make this risotto. To serve 4:
See Also
Other recipes from Versilia, the Tuscan coastal plain
About risotto and other risotto recipes
About clams and mussels