These crabs have a squarish shell which is tapered behind and has a marginal notch. The Sand Fiddler and the Mud Fiddler are both found in strongly brackish to saltwater salinities. The Brackish-water Fiddler is found in freshwater to mildly brackish marshes. While they occupy similar habitat, the Mud Fiddler is more common on mud flats while the Sand Fiddler is found on sandy substrates and on beaches. All three species range from Cape Cod to Texas but the Mud Fiddler is absent in Florida south of St. Augustine.
Fiddlers burrow into flats and banks in or near coastal marshes.
Fiddlers are active by day, feeding mainly on bacteria, minute algae, and fermenting marsh plants obtained from the soil. These species are not currently threatened or endangered.