136 W. H. BURT 



to count names in a list and talce them at their face value. They then 

 formulate hypotheses on what they innocently, but erroneously, 

 think are substantial data. 



These and other problems have confronted me in the preparation 

 of this paper, and I have found no good solution to them. I have 

 tried various formulas for taxonomic resemblance, and will discuss 

 some of these presently. However, no formula will give a correct 

 answer unless the basic data are accurate. If we must use a formula, 

 and this method has great popularity in biology today, I prefer 

 one that takes into account the entire faunas, not just the smaller 

 of two. The latter may be best for fossil faunas, as Simpson (1947) 

 seems to think, but for our purposes I believe there are better ones. 

 After counting the species and genera listed in the literature, 

 primarily in Miller and Kellogg (1955) for North America, Ellerman 

 and Morrison-Scott (1951) for Asia, and Cabrera and Yepes (1940) 

 for South America, I decided to use the genus as my category for 

 the application of the various formulas. I have also prepared a 

 chart in an attempt to show graphically the relationships of these 

 three faunas. Other authorities were also consulted, and when there 

 was disagreement on a generic name, I arbitrarily included or ex- 

 cluded the name as I thought best. The numbers used, therefore, 

 should be considered approximate. I then employed "taxonomic 

 intuition." With this system, I came up with similar, but somewhat 

 different results. Neither system is accurate, but they show the same 

 general trends which fit the concepts of every competent mammalo- 

 gist today. My objective here is to test different methods of indi- 

 cating taxonomic resemblance — to discover, if possible, how nearly 

 accurate they are and where they might be misleading. I shall 

 attempt to analyze some of these, but first I should like to indicate 

 some of the perplexing problems that confront one in this kind of 

 effort. 



To begin with, our knowledge of the three faunas under con- 

 sideration is not equal, so our basic data are not equivalent, and 

 this in itself makes comparisons difficult. Our knowledge is best for 

 North America, but even here we have many names in the literature 

 that no doubt will be omitted from the books in another twenty-five 

 years or so. As a matter of fact, our total knowledge of any one kind 

 of mammal is inadequate to evaluate it properly in the whole 

 scheme of things. 



