It doesn't take long for visitors to the Cape Ann peninsula in northern Massachusetts to figure out what the local specialty is. Here, on a stretch of land every bit as scenic and charming as that of Cape Cod to the southeast, clam shacks are more abundant than fast-food joints. But not just any clams are on offer: On Cape Ann, soft-shells (also called long-necks, steamers, or just mud clams) are king. These clams (Mya arenaria), easily identifiable by the long, rubbery siphons, or necks, that protrude from their thin, brittle, elongated shells, are foundall along the East Coast, from Maine to North Carolina, and as far afield as Britain and France. Most clam lovers, though, myself included, are partial to the exceptionally sweet and tender ones harvested from the mud flats off Ipswich, on the edge of Cape Ann. One taste of these particular Ipswich clams makes it very clear that not all soft-shells are created equal.