[166] See W.K. Parker, "On the Structure and Development of the Skull in the Pig." Phil. Trans. pp. 289-336, 1874.
[167] See W.H. Flower, "On the value of the characters of the base of the cranium in the classification of the order Carnivora." P.Z.S. 1869, p.
[168] See W.K. Parker, Monograph of the shoulder-girdle and sternum of the Vertebrata, Ray Soc. 1868.
[169] See p. 405.
[170] See E. Lydekker, P.Z.S. 1895, p. 172.
[171] See H. Wincza, Morph. Jahr. XVI. p. 647, 1890.
[172] See K. Bardeleben, P.Z.S., 1889, p. 259.
[173] See E. Cope, "The origin of the foot structures of Ungulata," Journ. of Philad. Acad. 1874. H.F. Osborn, "The evolution of the Ungulate foot," T. Amer. Phil. Soc. 1889.
[174] See O.C. Marsh, various papers including "Fossil horses in America," Amer. Natural. 1874; "Polydactyl horses," Amer. J. Sci. 1879 and 1892. M. Pavlow, "Le développement des Equidés," Bul. Soc. Moscou, 1887, and subsequent papers in the same. Osborn and Wortman, "On the Perissodactyls of the White River beds," Bull. Amer. Mus. Dec. 23rd, 1895.
[175] See H.F. Osborn, Chalicotherium and Macrotherium, Amer. Natural. 1889—91—92.