The organic-walled microfossil Mispertonia desiccata gen. et sp. nov. is described from the Arnsbergian (Mississippian, Early Carboniferous) of borehole Kirby Misperton-1, North Yorkshire, UK. This species includes thin-walled, originally spherical or sub-spherical vesicles; with a single polygonal field surrounded by a rim and a thickened collar which is interrupted by grooves radiating out from the angles of the polygonal field. The form is recovered from marine strata of the Silsden Formation equivalent, but is not necessarily of marine origin. Similar specimens, here synonymised with M. desiccata, are known from the non-marine Late Permian or Early Triassic of India.