34 PLEISTOCENE MAMMALIA. 



in the lower jaw and being accompanied by a largely increased size in the case of 

 one or more of the remaining pairs of incisors and of the canines. 



The most primitive form of mandible is shown by H. iravaticus, in which the 

 long narrow symphysis, three pairs of small incisors and small canines indicate 

 an animal much closer to the pigs than any other species of which the mandible is 

 preserved. The next step is seen in H. sivalensis, in which the symphysis is 

 considerably shorter, though the incisors still preserve their small size. The third 

 stage is found in H. namadicus, in which the symphysis has still more decreased in 

 length, while i. 2 has become slightly smaller and is thrown more or less above the 

 level of the other two. Lastly, in H. palseindicus the symphysis is shorter than in 

 any other form, while i. 1 and i. 3 have increased enormously in size at the 

 expense of i. 2. It is tempting to consider that H. amphibius was derived from 

 H. palseindicus by the final disappearance of i. 2, but, as has already been pointed 

 out, the specimen No. 1873 in the Royal College of Surgeons Museum would seem to 

 prove that the persisting teeth in H. amphibius are i. 1 and 2, and further, Lydekker 

 maintains that the long mandibular symphysis of H. amphibius shows that it could 

 not have been derived from any of the Indian species. Its origin may perhaps be 

 sought in the hexaprotodont H. hipponensis described by Gaudry 1 from Bone, 

 Algeria. In H. (Ghoeropsis) Uberiensis another incisor, probably the small one 

 of H. amphibius, has disappeared. 



Although Cuvier in the first instance believed the fossil hippopotamine bones 

 to belong to H. amphibius, he quickly altered his opinion, considering that the 

 fossil bones belonged to a larger extinct species which he named 77. major. He 

 was followed in this opinion by Nesti, Owen, Falconer, Forsyth Major, and 

 originally by Boyd Dawkins. 



The features in the fossil form on which these authors relied in separating it 

 from the living species are — the larger size ; wider interval between the second 

 and third premolars ; posterior position of the orbit ; shortness of the cranium ; 

 greater elevation of the sagittal and occipital crests ; excessive elevation of the 

 upper margin of the orbit above the plane of the brow. Cuvier also states that 

 the neck is shorter than in the living species, and that the width of the combined 

 radius and ulna is only one-and-a-half times the length of the radius, instead of 

 twice, as in the living species. By 1885 Boyd Dawkins was convinced as to the 

 specific identity of H. major and H. amphihius, and many later writers, including 

 Lydekker, have adopted the same view. De Blainville had arrived at the same 

 conclusion as early as 1844. Osborn, however, in ' The Age of Mammals ' (1910), 

 retains the distinctive name E. major for the large fossil form, as does Forsyth 

 Major (1896). 



1 ' Bull. Soc. G-eol. France' [3], iv (1876), p. 501. 



