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  1. The nature of shield abnormalities in the turtle shell / [by] Rainer Zangerl -- and Ralph G. Johnson --.
    By: Zangerl, Rainer, - Johnson, Ralph Gordon,
    Publication info: [Chicago] :Chicago Natural History Museum,1957.
    Contributed by: Field Museum Library
    BHL Collections: Field Museum Library
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  2. New fossil polychaete from Essex, Illinois / Ida Thompson -- and Ralph G. Johnson --.
    By: Thompson, Ida. - Johnson, Ralph Gordon,
    Publication info: Chicago :Field Museum of Natural History,1977.
    Contributed by: University of Illinois Urbana Champaign
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  3. Pennsylvanian invertebrates of the Mazon Creek area, Illinois: the Essex fauna and medusae / Ralph Gordon Johnson -- and Eugene S. Richardson, Jr. --
    By: Johnson, Ralph Gordon, - Richardson, Eugene Stanley,
    Publication info: [Chicago] :Field Museum Press ,1968.
    Contributed by: University of Illinois Urbana Champaign
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  4. Pennsylvanian invertebrates of the Mazon Creek Area, Illinois: the morphology and affinities of Tullimonstrum / Ralph Gordon Johnson -- and Eugene S. Richardson, Jr. --
    By: Johnson, Ralph Gordon, - Richardson, Eugene Stanley,
    Publication info: [Chicago] :Field Museum of Natural History ,1969.
    Contributed by: University of Illinois Urbana Champaign
    View Book