CLASSIFICATION OP THE MAMMALIA 55 



superorder and others, while above the class comes the sub- 

 kingdom of Vertebrata, or animals with internal skeletons, 

 which includes mammals, birds, reptiles, amphibians and 

 fishes. 



A word should be said as to the conventions of printing 

 technical names. The names of all species are, in American 

 practice, printed in small letters, but many Europeans write 

 specific terms which are proper nouns or adjectives with a 

 capital. Generic, family and all groups of higher rank are 

 always written with a capital, unless used in vernacular form, 

 e.g. Artiodactyla and artiodactyls. It is also a very general 

 custom to give capitals to vernacular names of species, as the 

 Mammoth, the Coyote, the Black Bear. Genus and species 

 are almost invariably in italics, groups of higher rank in roman. 



Such a scheme of classification as is outlined above has a 

 decidedly artificial air about it and yet it serves a highly use- 

 ful purpose in enabhng us to express in brief and condensed 

 form what is known or surmised as to the mutual relationships 

 of the great and diversified assemblage of mammals. The 

 scheme has been compared to the organization of an army into 

 company, battalion, regiment, brigade, division, army corps, 

 etc., and there is a certain obvious likeness; but the differences 

 go deeper, for an army is an assemblage of similar units, 

 mechanically grouped into bodies of equal size. A much closer 

 analogy is the genealogical or family tree, which graphically 

 expresses the relationships and ramifications of an ancient and 

 wide-spread family, though even this analogy may easily be 

 pushed too far. Blood-relationship is, in short, the under- 

 lying principle of all schemes of classification which postulate 

 the theory of evolution. 



The system of Linnaeus, as expanded and improved by 

 modern zoologists, has proved itself to be admirably adapted 

 to the study of the living world ; but it is much more difficult 

 to apply it to the fossils, for they introduce a third dimension, 

 so to speak, for which the system was not designed. This 



