SYSTEMATIC DISCUSSION 



We have not considered it necessary, in a work of this sort, to 

 enter into all the refinements of modern zoological classification and 

 nomenclature, as the names of orders, families and other groups are 

 herein used only for the purpose of bringing certain groups of species 

 together and discussing their economic status, not for the purpose of 

 exhibiting their physical relationships. Indeed, it would be impossible 

 to conform exactly to all the modern systems of classification, as there 

 is too much difference of opinion among the various authorities. The 

 relationship of organisms is not end on end, but rather, in a general 

 sense, in the form of a tree, hence strictly accurate and logical classifi- 

 cation and arrangement end on end in a book or a list is impossible. 

 Furthermore, too much yet remains to be learned for anyone to say 

 the final word as to classification or nomenclature. We hope to be par- 

 doned if in some instances we have used terms familiar to those not 

 engaged in technical taxonomy, but not approved by some taxonomists. 

 It has not been our intention to include all known families or other 

 groups of mammals, but we have endeavored to include all groups of 

 economic importance in North America north of Mexico, with many 

 from foreign countries. 



ORDER MONOTREMATA PRIMITIVE EGG-LAYING MAMMALS 



This, the lowest order of mammals, is confined to the Australasian 

 region, where it is represented by about four living species. Though 

 of but little economic consequence, it is of very great scientific interest. 

 The food of the duck-billed platypus (Orniihorhynchus anatinus) 

 is said to consist of aquatic insects, small crustaceans, worms and the 

 like. The spiny anteaters (Echidna, 3 species) feed chiefly upon ter- 

 mites ("white ants"), for which their long snouts and longer, slender, 

 glutinous tongues are specially adapted. 



ORDER MARSUPIALIA OPPOSSUMS, KANGAROOS 

 AND THEIR ALLIES 



This order, much more generally distributed in the geological past, is 

 now greatly restricted in range and reduced in number of species, yet 

 the economic importance of the order is considerable, not only because 



