Phylum [Vertebrata] Lamarck, 1801 see Infraphylum Vertebrata Lamarck, 1801 Class Agnatha Cope, 1889 Subclass †Cephalaspidomorphi Kiaer & Stensiö, 1920 see Class Agnatha Cope, 1889 Order †Osteostraci Lankester, 1868 - osteostracans see Order Cephalaspidiformes Halstead Tarlo, 1967 Genus †Dartmuthia Patten, 1931