Type material for 60 nominal species of fossil chelicerates are in the Invertebrate Paleontology Collections of Yale University's Peabody Museum of Natural History. Primary types for 46 nominal species include 41 holotypes, and 5 syntypes (representing 3 nominal species). Secondary types for 15 nominal species include 31 paratypes. Tertiary types of 19 nominal species include 35 hypotypes. Most types are from Mazon Creek (Illinois), Warren (Pennsylvania), Elmo (Kansas) and Buffalo (New York) and have been described by C.E. Beecher, James Hall, E.N. Kjellesvig-Waering and Alexander Petrunkevitch.