AN INTRODUCTION" 



TO 



THE STUDY OF MAMMALS 



LIVING AND EXTINCT 

 CHAPTEE I 



INTRODUCTORY REMARKS 



Mammalia (French, Mammifkres ; German, Sdugethiere) is the name 

 invented by Linnaeus (from the Latin mamma), and now commonly 

 used by zoologists, for one of the five great classes of vertebrated 

 animals, which, though the best known and undoubtedly the most 

 important group of the animal kingdom, has never received any 

 generally accepted vernacular designation in our language. The 

 unity of structure of the animals composing this class, and their 

 definite demarcation from other vertebrates, were not recognised 

 until comparatively modern times, and hence no word was thought 

 of to designate what zoologists now term a mammal. The nearest 

 equivalents in common use are "beast" and "quadruped," both of 

 which, however, cover a different ground, since they are often used 

 to include the larger four-footed reptiles, and to exclude certain un- 

 doubted mammals, as Man, Bats, and AVhales. 



The limits of the class as now understood by zoologists are 

 perfectly well defined, and, although certain forms still existing on 

 the earth (but not those mentioned above as excluded by the popular 

 idea) are of exceedingly aberrant structure, and exhibit several well- 

 marked characters connecting them with the lower vertebi'ated 

 groups, common consent retains them in the class with which the 

 great proportion of their characters ally them, and hitherto no 

 traces of any species showing still more divergent or transitional 

 characters have been discovered. There is thus an interval, not 

 bridged over by any known forms, between mammals and other 



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