AMERICAN RUMINANT-LIKE MAMMALS, 259 



orders have in common must have been independently acquired 

 by each. Startling as such a statement may seem to many, 

 there is no escape from it, even though the position which has 

 here been assigned to -such genera as Leptomeryx, Protoceras, 

 the oreodonts, etc., be an altogether mistaken one. We can 

 now trace the history of the main tylopodan phylum, step by 

 step, back to the Uinta epoch, and the Uinta representative of 

 the series, Protylopus, has no pecoran features, save only the 

 selenodont molars. As we may feel perfectly confident that 

 Protylopus is not ancestral to the Pecora or any part of them, 

 it follows that characters common to the two suborders, but 

 not found in the Uinta genus, must have been separately de- 

 veloped. Riitimeyer long ago pointed out, from* a comparative 

 study of the recent forms, that the camels and llamas were 

 but distantly connected with the true ruminants, and his masterly 

 work on these questions is abundantly confirmed by the Ameri- 

 can fossils, which were very imperfectly or not at all known 

 when he wrote. 



The conclusions which we have reached suggest the impor- 

 tance of giving due weight to geographical considerations in 

 dealing with phylogenetic and taxonomic problems. A little 

 study and experience enable the observer to detect the- foreign 

 and migrant elements in a fauna, even though they firmly 

 establish themselves in their new home and there give rise to 

 new branches. When isolated genera are found, one of the 

 most important questions which arises concerning them is, are 

 they most like the types of this or of some other continent? 

 This question rightly answered will serve as a most valuable 

 clue in following out the history of the genus. Riitimeyer 

 seems to have been guided largely by geographical consid- 

 erations in the statement that I have mentioned as to the 

 importance of the Tylopoda in North American life, and I am 

 thoroughly convinced of the value of such criteria. Hitherto 

 we have ignored them entirely too much. 



I am perfectly conscious that I have been asking you to 

 accept a great deal upon my ex-cathedra statements ; but the 

 difficulty lies, not in the absence of evidence, but in the impos- 

 sibility of producing that evidence in court. It can be gained 



