SIWALIK AND NARBADA BUNODONT SUINA. 
3—37 
'Number of species. — The followinp^ list comprises the non-Indian species of the 
genus ; and indicates the variation in the number of incisors : — 
1. HirpopoTAMUs AMPHiBius, Liiiii. Up. pliocene to recent, Europe and Africa. 
H. abyssinicus. Less. H. major, Cuv. 
H. annectans, Falc. H. senegalensis, Desm. 
H. capensis, Desm. Tttraprotodon amphibius, Falc. 
Tetraproiodon rnajor, Falc. 
I. I : the inner pair much larger than the outer : one instance is recorded of three 
incisors in one ramus of the mandible. i 
2. Hippopotamus hipponensis, Gaudiy.^ Pleistocene’ (?), xilgeria. 
Hexapioiodon hipponensis, Gaud. 
I. |. A small species, distinguished by the smooth enamel of the lower incisors ; 
which tend to expand at their extremities, and thus indicate affinity with the pigs. 
3. Hippopotamus libeeiensis, Morton. Recent, W. Africa. 
Chceropsis liberiensis, Leidy.® Teiraprotodoji liberiensis, Falc. 
I. Much smaller than H. amphibius. 
4. Hippopotamus minutus, Cuv. 
Tetraprotodon minutus, Falc. 
I. t. Considered by Gervais^ to be closely allied to H. liberiensis. 
5* Hippopotamus pentlandi, H. von Meyer. Pleistocene, S. EurojDC. 
Tetraprotodon pentlandi, Falc. 
I. \. As large as H. amphibius, with which Prof. Gaudry^ thinks it may be identified. 
II. medius, dviY .=IIalitherium. 
Distribution. — The genus is confined to the Old World, where it formerly had a 
wide distribution : its earliest appearance in Europe is in the upper pliocene. 
Species 1 : Hippopotamus sivalensis, Falc. and Caut. 
Syn. Eexaprotodon sivalensis^ F. and C. 
History. — This species was originally described by Falconer and Cautley® in 
1839 on the evidence of a very perfect specimen of the cranium from the Siwaliks ; 
which, with numerous other specimens, was subsequently figured in the “ F.A.S.”^ 
At a later date the species was subdivided by M’Clelland,® but apparently on 
insufficient grounds. The name Hexaprotodon was originally applied by Falconer 
and Cautley in a sub-generic sense, but was adopted as a generic term by Sir R. 
Owen.® 
1 Gaudry, ‘ Bui. Soc. Geol.,’ ser. 3, vol. 4, p. 504. Falconer (“ Pal. Mem.,” vol. II., p. 406) records another so-called 
instance of hexaprotodontism. The specimen on which this statement rests is in the Museum of Trinity College, Dublin, 
where the present wi'iter has examined it ; the extra tooth is malformed and very small, and situated on the alveolus of the 
canine. It can be in no sense regarded as a reversion, hut is merel}' a redundancy : the additional incisor of the 
hexaprotodont form should occur between the two incisors of the living hippopotamus. 
2 Op. cit., p. 601, pi. XVII. 3 ‘ Journ. Acad. Philadel.,’ vol. II., 1853, p. 207. 
4 “ Zool. et Pal. Gen.,” 1st ser., p. 250. 5 Op. cii., p. 504. 
6 ‘ Asiatic Eesearches,’ vol. XIX., p. 39. ” Pal. Mem.,” vol. I., p. 130, pis. XI., XII. 7 Plate LIX., et. seq. 
9 ‘ Journ. As. Soc. Beng.,’ vol. VII., p. 1038 : it is unnecessary to quote M’Clelland’s names. 
3 “ Odontography,” p. 666, pi. CXLIII. 
B 
