
No. 23, 
NORTH AMERICAN FAUNA. January, 1904. 



A LIST OF THE GENERA AND FAMILIES OF MAMMALS. 
3y T- S. PALMER, 
Assistant, Biological Survey. 
INTRODUCTION. 
HISTORY AND OBJECTS OF THE INDEX. 
9 
Since the publication of the tenth edition of the ‘Systema Naturee’ 
of Linneus, in 1758, the number of generic names of mammals has 
multiplied with ever-increasing rapidity. This fact can readily be 
appreciated if the intervening century and a half be divided into three 
periods of approximately even length: (1) 1758-1800, (2) 1801-1850, 
(3) 1851-1900. At the beginning of the first period only 39 genera 
were recognized, but at its close about 175 generic names had been pro- 
posed, of which probably less than 100 were recognized. At the end 
of the second period (1850) the number was approximately 1,200, and 
at the close of the third had increased to more than 4,000, of which 
1,840 were admitted by Trouessart as entitled to recognition. In 1901 
more than 100 new generic names were added to the list. 
This rapid increase in the number of names has been due partly to 
increased activity in systematic work, partly to subdivision of older 
groups of mammals, partly to duplication of names through inad- 
vertence or otherwise, but more especially to the marvelous develop- 
ment in paleontology. Of the genera described before 1800, only 
three— Mammut, Megalonyx, and Megatherium—belong to extinct 
groups. <A few years later this number was augmented by the names 
of numerous forms described from the Paris basin; since then, by the 
names required for the hosts of extinct mammals described from the 
deposits of France, Germany, Greece, India, Australia, the United 
States, and Argentina. 
Investigation has shown the necessity of subdividing older groups, 
as the older generic limits were too broad to permit grouping forms 
with sufficient precision. As a result, the genus of to-day is much 
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