150 



Dr. W. Kowaievsky on the 



[Feb. 6, 



ture of the skeleton is objectionable in the highest degree ; besides, in 

 this classification there is no room for those fossil genera which are cer- 

 tainly not Suina, and most probably did not ruminate. The greater the 

 number of such genera, the better their organization and history are known, 

 the more pressing the necessity to give them some adequate place in our 

 zoological system. As an instance that such a necessity is keenly felt,we may 

 cite Professor Leidy, who, in describing the Oreodontidce, Agriochceridce, &c. 

 of Nebraska, says that they were " ruminating hogs but in reality they 

 were not hogs at all, and most probably did not ruminate ; what is, then, to 

 be done with them ? 



The introduction of Professor Owen's* strict division between Paridi- 

 gitata and Imparidigitata was a great gain to science ; it radically sepa- 

 rated two groups that previously were always hopelessly mixed together ; 

 but now the same principle must be carried further. The separation of the 

 two groups of Paridigitata and Imparidigitata took place in very ancient 

 time, not nearer than the Cretaceous period, and the striking diversity 

 exhibited by both groups from the lowest Eocene is a proof of their ancient 

 separation. But one of the branches, the Paridigitata, in its turn, split 

 very anciently again into two distinct groups, one with tubercular, the 

 other with crescentic teeth. This occurred at nearest in the Lower Eocene, 

 perhaps even in the Cretaceous period. These groups, once separated, 

 kept entirely apart and followed different lines of descent, although the 

 modifications which both undergo along the descending lines are parallel 

 and analogous even to the greatest details. Following these two divergent 

 lines of descent, both groups culminate in the recent fauna in such forms 

 as the PhacocJiosrus and Dicotyles for one group, and the Bovidce for the other. 



Lower Cretaceous Ungulata. 



Parid. with Parid. with 



tuberc. teeth. crescentic teeth. 



Links between them we discover none ; and to discover their parentage, 

 we must pass along the ascending lines to the point at which they diverge, as 

 the linking genera, which doubtless existed at the time of separation, are long 

 ago extinct, and both groups are now widely separated. I suggested 

 this view, whilst studying in the British Museum the remains oiHyopota- 

 midce, to Professor Owen, and he finds no objection to it. He aided me 

 * Proposed before him by French anatomists, but never carried out completely. 



