Semper, Animal Life, Intern. Sci. Series, London, 1881, p. 172.
Miklucho-Maclay, Jen. Zeitsch. iii. 1867, p. 448.
Wiedersheim, Lehrb. d. vergl. Anat. d. Wirbelth. ed. 2, Jena 1886, p. 616.
The glottis is furnished with a structure analogous to the epiglottis-like plate of Protopterus (Wiedersheim, op. cit. p. 616).
Balfour and Newton Parker, Phil. Trans. 173, Part ii. 1883, p. 425.