404 



HIPPOPOTAMUS. 



VI. NOTE ON THE EXISTING HIPPOPOTAMUS LI- 

 BERIENSIS (MOETON), WITH A SYNOPSIS 

 OF THE HIPPOPOTAMID^], FOSSIL AND 

 RECENT. 1 



Dr. Morton's discovery is one of the most interesting and remarkable 

 made in Zoology during the present century. Cuvier, in his ' Discours 

 Preliminaire,' has entered into an elaborate argument against the 

 probability of any . remarkable existing large species of land animal 

 remaining' to be discovered, after the search 'which has been made 

 through the continents and great islands of the globe. Dr. Morton's 

 discovery proves that the inference was premature. 



Hippopotamus Liberiensis is perfectly distinct from II. amphibius. 

 It differs more from the latter than H. amphibius does from H. major 

 and H. palmndicus, the only two fossil species of the same subgenus 

 of which the crania are known. The distinctive characters are very 

 strongly marked, and are chiefly the following, viz. the length of the 

 cranium proper as compared with that of the face ; the advanced po- 

 sition of the orbits, which are nearly in the middle of the head ; the 

 convexity of the forehead, both from back to front and across the' orbits; 

 the less hooking forwards of the leafy expansion and the greater eleva- 

 tion of the coronoid process of the lower jaw, as well as the absence of 

 any diasteme. The dental characters are also different. The trefoil 

 disc of wear in the true molars is exactly as in Hippopotamus amphibius, 

 but the canine teeth of the upper jaw alone, without reference to the 

 dimensions and other peculiarities, would establish the distinctness of 

 the species. In H. amphibius and H. major, the internal vertical 

 channel is shallow, while in //. Liberiensis it is so deeply grooved as 

 to yield a strongly marked reniform outline in the section. This cha- 

 racter is of especial interest, as it is constant and nearly to the same 

 amount as in. an Indian fossil species of the subgenus Hexapro*odon, 

 viz. H. Sivalensis. The lower tusks resemble closely those of H. am- 

 phibius in form and direction. There are four incisors in the upper 

 jaw which are slightly curved and nearly vertical. In the lower jaw 

 there are only two incisors, which are much stronger than those in the 

 upper jaw and project almost horizontally forwards. It would appear 

 to be the intermediate incisor which is alone developed on either side. 



1 In 1847 Dr. Morton transmitted his 

 specimens to London, to be examined 

 by Dr. Falconer, who contributed the 

 greater part of this note to Dr. Mor- 

 ton's essay which was published at 

 Philadelphia in 1849. Additions have 



been made to the original note from the 

 author's Note-books. The Synopsis of 

 HippopotamidcB and the Memorandum 

 of the Hippopotamus skull at Dublin 

 have also been extracted from the Note- 

 books. — [En.] 



