TAXEOPODA. 381 



known Taxeopoda possess. I refer to the absence of the trochlea, a character 

 which will yet be discovered in the Taxeopoda, 1 have no doubt. 



The Taxeopoda approach remarkably near the Bunotheria, and the 

 ungiiiculate and ungulate orders are brought into the closest approxima- 

 tion in these representatives. In tact I know of nothing to distinguish 

 the Condylarthra from the Mesodonta, but the ungulate and unguiculate 

 characters of the two divisions. In the Creodonta this distinction is reduced 

 to very small proportions, since the claws of Mesomjx are almost hoofs. 

 Some of the genera allied to Periptychus, present resemblances to the Creo- 

 donta in their dentition also. 



The facts already adduced throw much light on the genealogy of the 

 Ungulate Mammalia The entire series has not yet been discovered, but 

 we can with great probability supply the missing links. In 1874 I pointed^ 

 out the existence of a yet undiscovered type of Ungulata, which was 

 ancestral to the Amblt/poda, Proboscid^a, Perissodactyla, and Artiodadyla, 

 indicating it by a star only in a genealogical table. This form was discov- 

 ered in 1881, seven years later, in the Condylarthra. It was not until latei*^ 

 that I assumed that the Diplarthra are descendants of the Amblyjwda,. 

 although not of either of the known orders, but of a theoretical division 

 with bunodont teeth.^ That such a group has existed is rendered extremely 

 probable in view of the existence of the bunodont Proboscidea and Condy- 

 larthra. That the Taxeopoda was the ancestor of this hypothetical group a* 

 well as of the Proboscidea, is extremely probable. But here again neither 

 of the sub-orders of this group represent exactly the ancestors of the known 

 Amblypoda, which have an especially primitive form of the astragalus not 

 found in the former. In the absence of an ankle-joint, the Pantodonta are 

 more primitive than any other division of the Ungulata, and their ancestors 

 are not likely to have been more specialized than they. It is probable that 

 a third sub-order of Taxeopoda has existed which had no trochlea of the 

 astragalus, which I call provisionally by the name oi Platyarthra. 



The preceding paragraphs were written in May of the year 1882^ 



'Homologies and Origin of Teeth, etc., Journal Academy Nat. Science, Philada., 1874, p. 20. 



^Report U. S. Geol. Survey W. of 100th Mer., p. 28^, 1877. 



^This hypothetical sub-order is called in the above scheme Amblypoda hyodouta. 



