Article: The Permian brachiopod genus Horridonia Chao
Horridonia is redefined to include two variable species, H. horrida and H. timanica. The lectotype of the former is redescribed and figured. H. timanica is a Russian and Arctic species, H. horrida European. Both species occur in Greenland. The genera Sowerbina Fredericks emend. Dunbar and Pleurohorridonia Dunbarare considered synonymous with Horridonia.