[50] T.H. Huxley, Amphibia (Encyclopaedia Britannica).
[51] See R. Wiedersheim, Morphol. Jahrb. Bd. III. 1877, p. 459.
[52] See A. Fritsch, Fauna der Gaskohle, Prague, 1883-85-86, also writings of Cope, Credner, Huxley, H. v. Meyer, Miall.
[53] See R. Wiedersheim, Anatomie der Gymnophionen, Jena, 1879.
[54] i.e. between one vertebra and the next.
[55] See A. Ecker, Die anatomie des Frosches, Braunschweig 1864, translated by G. Haslam, Oxford, 1889, also A.M. Marshall, The Frog, 5th edition, Manchester and London, 1894.
[56] W.K. Parker, Phil. Trans. 161, 1871, p. 137, and W.K. Parker and G.T. Bettany, The Morphology of the Skull, London, 1877, p. 136.
[57] See G.B. Howes and W. Ridewood, P.Z.S., 1888, p. 141.
[58] See bottom of p. 187.
[59] O. Hertwig. Ueber das Zahnsystem der Amphibien. Arch. mikr. Anat. supplem. Bd. XI. 1875.