Thus, shipwrecks are protected from the ravages of shipworms. Another source of damage comes from wood boring fauna, such as shipworms and Limnoria. Kuphus is a genus of shipworms, marine bivalve molluscs in the family Teredinidae. It lacks the cecum which in other shipworms holds symbiotic bacteria which digest wood. Lithoredo have differently shaped teeth than shipworms which can finely grind stone. The order includes such bivalves as soft-shell clams, geoducks and shipworms. Shipworms (Teredolite) are wood-boring bivalves that burrow deeply into submerged wood. Most shipworms are relatively smaller and feed on rotten wood. The valves of shipworms are separated and the aperture of the mantle lies between them. Further bridges succumbed to flood and shipworms, the last timber bridge collapsing in 1929. In 1916, at the request of the U.S. Navy he started a study of shipworms. Shipworms also damaged the ships in tropical waters. Shipworms are marine animals in the phylum Mollusca, order Bivalvia, family Teredinidae. Within maritime environments one of the largest pest threats to waterlogged wood includes shipworms ("Teredinidae"). In 2017, the shipworms were formally researched on by local and international scientists.