Shipshells are a kind of huge scaphopod (tribe Barcines). There are multiple species, ranging from 5 to 35 mestres in shell length.
Unlike common scaphopods, shipshells are not fossorial and rarely are benthic. Most species float on the ocean surface and lead a planktonic life-cycle (though they can swim if necessary). The shell has the shape of a ship's hull, as does the foot. Usually, shipshells will drift (or swim) backwards, catching microplankton with their many captacula.
Most shipshells have symbiotic relationships with birds and pterosaurs, which clean their shells in exchange for a safe nesting and resting spot. Shipshell shells are unusually resistant to acid, a necessary design element for enduring constant guano dejects.
Shipshells usually avoid storms and coasts, as well as underwater cities.