The Saccocirridae are small interstitial polychaetes common in coarse sand on reflective, surf beaches, usually within the zone of retention. Saccocirridae have a worldwide distribution and many more species likely remain to be described. These polychates are usually between 2 and 10 millimetres (0.08 and 0.39 in) in length and 500 μm wide. They have reduced parapodia and are considered a true interstitial species, incapable of burrowing through finer sediments.

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