A HISTORY OF LAND MAMMALS IN 

 THE WESTERN HEMISPHERE 



CHAPTER I 



METHODS OF INVESTIGATION — GEOLOGIGAL 



The term Mammal has no exact equivalent in the true 

 vernacular of any modern language, the word itself, like its 

 equivalents, the French Mammifere and the German Sduge- 

 thier, being entirely artificial. As a name for the class Linnaeus 

 adopted the term Mammalia, which he formed from the Latin 

 mamma {i.e. teat) to designate those animals which suckle 

 their young ; hence the abbreviated form Mammal, which has 

 been naturalized as an English word. ''Beast," as employed 

 in the Bible, and ''Quadruped" are not quite the same as 

 mammal, for they do not include the marine forms, such as 

 whales, dolphins, seals, walruses, or the flying bats, and they 

 are habitually used in contradistinction to Man, though Man 

 and all the forms mentioned are unquestionably mammals. 



In attempting to frame a definition of the term Mammal, 

 it is impossible to avoid technicalities altogether, for it is the 

 complete unity of plan and structure which justifies the in- 

 clusion of all the many forms that differ so widely in habits 

 and appearance. Mammals are air-breathing vertebrates, ivhich 

 are warm-blooded and have a 4-chambered heart; the body cavity 

 is divided into pleural arid abdominal chambers by a diaphragm ; 

 except in the lowest division of the class, the young are brought 

 forth alive and are always suckled, the milk glands being universal 

 throughout the class. In the great majority of mammals the body 



