PERISSODACTYLA. 601 



the others ; it is never present in the pes. They have short necks and legs 

 and a very thick skin with scanty hair, and often folded so as to give them 

 the appearance of being armoured. The horns are purely epidermal 

 structures without bony core ; they have been compared to a mass ol 

 agglutinated hairs. The anterior horn is on the nasal bones, the posterior, 

 which is absent when there is only one, on the frontals. The stomach is 

 simple, the villi of the small intestine long, there is no gall bladder. The 

 testes hardly project, the uterus is bicornuate and the two mammae 

 inguinal. 



They are stupid timid animals, but ferocious when attacked. They 

 often inhabit swampy regions and like wallowing in water or mud. At 

 the present day they are found in Africa, the Malay Islands, and tropical 

 India. They are known fossil from the U. Eocene onwards in the Old and 

 New Worlds, but they become extinct in America at the end of the Pliocene. 

 There is but one living genus, Rhinoceros L. (including the genera Cera- 

 torhinus Gray and Atelodus Pom. ), the incisors are variable and often fall 

 out early, there are no upper canines, the peculiar cutting teeth of the 

 front of the lower jaw are probably canines, p % m | ; the first milk 

 molar is smaller than the others and not always replaced ; the grinders 

 form roots early and the valleys are not filled in with cement. Vertebrae 

 C 7, D 19-20, L 3, S 4, C about 22. Manus and pes with three hoofed 

 digits ; in the manus there is a rudiment only of metacarpal 5. 



The living species are R. unicornis L., India, with one horn ; R. son- 

 daicus Desm., with one horn, Java, India, etc. ; R. sumatrensis Cuv., 

 Malacca, Sumatra, Borneo, two horns ; R. simus Burchell, the white 

 rhinoceros, Africa, two horns ; R. bicornis L., Africa, two horns. Many 

 extinct species from, the Miocene of the Old World onwards. It is there- 

 fore like the tapir a very ancient type. R. antiquitatis Blumenb. (ticho- 

 rhinus Cuv.) is the woolly rhinoceros of the Pleistocene of Europe a huge 

 animal with two horns, the carcases of which with those of the mammoth 

 have been discovered in N. Siberia. 



A large number of fossil genera, which have been arranged in sub-families, 

 are known from the earlier tertiary strata of the Old and New Worlds from 

 the U. Eocene onwards. Many of the older of these forms are charac- 

 terised by having a complete dentition, premolars simpler than the molars, 

 and a fully developed, though slender digit No. 5 on the manus. It is 

 impossible to deal with these here, but one or two may be mentioned. 

 Hyrachinus Leidy, U. Eocene of N. Amer. with 4 toes on manus. Hyra* 

 codon Leidy, with 3 toes in manus, L. Miocene of N. Amer., both with 

 complete dentition, without horns and with longer limbs and neck, and in 

 their general build more resembling Anchitherium than modern rhino- 

 ceroses. Aceratherium Kaup., hornless, with i \ c % p % m %, and 4 toes 

 on the manus, from the U. Eocene of France and Pliocene of India ; 

 Diceratherium Marsh, with two horns, U. Miocene, N. Amer. Elas- 

 motherium Fisch., Pleistocene of Siberia, a huge beast with 2 horns, with 

 p '4 m $, enamel much plicated, very hypsodont and valleys filled with 

 cement ; Amynodon Marsh, is the type of an ancient and primitive group 

 from the U. Eocene of N. Amer. 



Here maybe placed provisionally the Titanotheriidae,* which depart in 



* Earle, A memoir upon the genus Palaeosyops Leidy and its allies, 

 Journ. A cad. Philadelphia, 9, 1892, p. 267. Osborn, Revision of the 

 genus Tdmatotherium, Bull. Amer. Mus. N. Hist., 1, 1895, p. 82, and 346. 



