81. ——. 1850. Die Labyrinthodonten aus dem Saarbrücken Steinkohlengebirge. Quarto, pls. 1-4.
82. Butts, Edward. 1891. Recently discovered footprints of the amphibian age in the Upper Coal Measure Group of Kansas City, Missouri. Kans. City Scientist, V, No. 2, 17-19, figs.
83. ——. 1891. Footprints of new species of amphibians in the Upper Coal Measure Group of Kansas City, Missouri. Kans. City Scientist, V, 44, figs.
84. Carus, J. Victor. 1875. Labyrinthodontia. Handbuch der Zoologie, Bd. I, 485-486.
85. Case, E. C. 1898. The significance of certain changes in the temporal region of the primitive reptilia. Amer. Nat., XXXII. No. 374, 69.
86. ——. 1900. The vertebrates from the Permian bone bed of Vermilion County, Illinois. Jour. Geol., VIII, 698-729, 5 plates.
87. ——. 1902. On some vertebrate fossils from the Permian beds of Oklahoma. 2d Biennial Rpt. Dept. Geol. and Nat. Hist. Territory Oklahoma, 1901-1902, 62-68.
88. ——. 1902. Paleontological notes. Jour. Geol., X, 256-261.
89. ——. 1903. New or little-known vertebrates from the Permian of Texas. Jour. Geol., XI, 394-402.
90. ——. 1907. Additional description of the genus Zatrachys Cope. Bull. Amer. Mus. Nat. Hist., XXIII, art. XXIX, 665-668.