32 ZOOLOGICAL RESEARCHES 



of the upper jaw two well developed incisors and an al- 

 veolus for a third incisor, which however is lost. 



The Lihevisin- Hippopotamus presents for the rest the 

 same number of premolars, molars and upper incisors as 

 the common H. amphibius ^ and in liheriensis like in am- 

 phibius the first molars always are the most used : this 

 very used condition of the first molars thus is not cha- 

 racteristic for Hberiensis as Prof. A. Milne Edwards men-, 

 tions (Recherches, T. I, p. 56). 



In conclusion , the difference between amphibius and li- 

 beriensis as to the normal number of teeth solely is , that 

 in amphibius there are 4 lower incisors and in Hberiensis 

 only 2 , and thus the dental-formulae run as follows : 



H. amphibius = 40 teeth. 



^ 2—1—4—3 



Ch. Hberiensis = 38 teeth. 



1 _ 1 _4 _ 3 



I think that in the Leyden Museum under the name of 

 amphibius there are at least two species brought together , 

 for I see such great differences in form and size of the 

 premolars and in form , size and direction of the incisors 

 in the skulls in our Museum , that I hardly can believe 

 that they belong to one and the same species, but un- 

 happily their origin is unknown or uncertain and their 

 number too small to solve this question for our specimens. 



That there are among the skulls of Ch. Hberiensis and 

 of H. amphibius some ones which have in one of the ra- 

 mus of the lower- or upper jaws three incisors indicates 

 that the ancestors of these two species had six lower 

 incisors and too six upper ones as we see now still in 

 their congeners belonging to the AS?<s-family. Therefore 

 N°. b mentioned above of my Cat. osteol. is so highly in- 

 structive. 



Of this interesting and rare species we now possess the 

 finest imaginable series , viz : an adult male with its skele- 

 ton, the skull of an adult female, a young male with 

 its skeleton and a very young male in alcohol. 



^otes from the Leyden Miuseuni, "Vol. X. 



