Burrowing deposit feeders that do not make permanent tubes. They are common in tidal flats and some attain dense population in sediments that are of mixed sands and mud. Their bodies are distinctive, with a well-developed and firm anterior region and a fragile and ragged-appearing posterior abdominal region bearing long, dorsally erect branchiae and parapodial lobes. Readily recognizable by their body form and characteristic camerated and crenulated setae.

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