Materials
Specimens in this study were collected by many different individuals from 1925 to 1989. Most were collected by P. A. Bungart or F. Thompson incidental to collection of Cleveland Shale fish material for the Cleveland Museum of Natural History (CMNH). All specimens studied were borrowed from the Cleveland Museum of Natural History, except for three specimens of Aptychopsis Barrande, 1872 which were kindly loaned by the Paleontological Institute of Lund, Sweden (LO), some of Ruedemann's type specimens provided by the American Museum of Natural History (AMNH), and Cooper's type specimens, which were borrowed from the National Museum of Natural History (USNM).
All the fossils studied from the Ohio Shale were preserved as carbonized films, flattened and compacted into the shale. Rarely was there a good interface between the specimen and the matrix, so preparation was held to a minimum. In a few cases folded specimens were separated from the rock along their outer surfaces. Most were prepared for photographic illustration by coating with finely particulate ammonium chloride. A few fragments were removed and coated with a thin film of gold for examination with the scanning electron microscope, but uncoated specimens were also examined by this technique with good results, probably due to their carbon content.
The USNM specimens, from the Woodford Shale of Oklahoma, are preserved as three-dimensional ellipsoidal packages of thin, sheetlike fossil material within phosphatic concretions from the shale matrix.