1873.] 



Osteology of the Hyopotamidse. 



149 



in the Middle or Lower Eocene of Mauremont, they existed until the 

 Lower Miocene period ; and judging by the great number of species 

 and genera, they must have filled in the fauna of this period the same 

 important place which the greatly diversified Ruminantia fill in the fauna 

 of our own times. Indeed the differentiation of Hyopotamidce may be 

 said to be even greater, in point of size, as they range from the Hyopota- 

 ?nus Henevieri, not larger than a rabbit, to the great Anthracotherium of 

 Eochette, which is as big as our Hippopotamus — all the intermediate stages 

 between these two extremes being represented by different genera, sub- 

 genera, and species of the same family. 



I hope that the rich development of this much neglected family will 

 arouse the attention of paleontologists, and that the skeletons of the dif- 

 ferent members will be more thoroughly investigated. For my own part, 

 though fully convinced that many of the Eocene Ryojpotamidce from 

 Mauremont and Egerkingen present, even in their teeth, characters 

 enough to separate them into distinct genera, I shall not do this, as the 

 multiplication of fossil genera, founded solely on dental characters, with- 

 out adequate knowledge of the skeleton, is more an obstruction than a 

 help to the progress of palaeontology. 



This refers to the Eocene Hyopotamidce of Mauremont and Egerkingen ; 

 for having found that among the Eocene members of this family there is one 

 which has lost its lateral digits and acquired a didactyle foot, very like an 

 Anoplotherium, I was obliged to separate this reduced form from its tetra- 

 dactyle congeners under the name of Diplopus (double foot), while the 

 tetradactyle species of the same family will form the genus Hyopotamus. 

 This diversity among the representatives of the same family is very inter- 

 esting ; something of the same kind is, however, to be found in our own 

 times in the Hyomoschus, subsisting side by side with the more reduced ru- 

 minants, though this is not an entirely parallel case. Moreover, as we have 

 in the Hyopotamidce, so to say, father and son existing together (the com- 

 plete form together with the reduced), and as, besides, this son bears a 

 great likeness in the typical structure of his limbs to the Anoplotherium, 

 we may infer that the fathers of both reduced forms bore also a general 

 likeness ; and this gives us a clue to the skeletons of the ancestors of 

 the Anoplotheridce, which is still further strengthened by many other 

 considerations, of which I speak more fully in my paper. 



Whilst trying to gain a more complete knowledge of the skeleton 

 of the extinct Paridigitata, I became convinced that we must make 

 some change in our zoological classification of the Ungulata in order to 

 admit the great quantity of genera which have no place in the pre- 

 sent system. After the breaking up of the Pachydermata (a name 

 that has long enough obstructed science and really checked progress by 

 holding together the most heterogeneous assemblage of animal forms), all 

 the Paridigitata came to be divided into Suina and Euminantia. This in- 

 troduction of a physiological function into a system based on the struc- 



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