PART II.—FAMILY AND SUBFAMILY NAMES OF MAMMALS. 
INTRODUCTION. 
A family has been defined as **a group of animals intermediate 
between the genus and order based on structural features of a more 
general character than the genus, while the limits are determined by 
the range and extent of the differential characteristies which exist 
between the typical form and the next allied. A family may there- 
fore be monotypic (i. e., limited to a single known species) or exceed- 
ingly polymorphic (i. e., embracing thousands of species)." ^ 
HISTORY." 
In the system of classification adopted by Linnsus in 1758 only 
four categories of organisms were recognized—classes, orders, genera, 
and species. In 1780 the number was increased to 11 by Storr, and 
numerous additions have since been suggested to meet the requirements 
of modern systematists. In fact, as shown by Gill, no less than 31 cate- 
gories have been proposed in the series beginning with the kingdom 
and ranging down to the individual.^ Of these 20 have been actually 
applied in the class Mammalia, and 18 in the class Pisces. Between 
order and genus the subdivisions, omitting the suborder, are 7 in 
number. Of these, however, none have come into general use except 
the family and subfamily. 
The term family as a subdivision of an order was apparently first 
used by Latreille, in 1796, in his * Précis des Caractéres génériques 
des Insectes. But the groups to which he gave the name were desig- 
nated merely by numbers, and it was not until ten years later, in his 
‘Genera Crustaceorum et Insectorum,' published in 1806, that the 
families were systematically named. Meanwhile, in 1798, Cuvier, in 
his ‘Tableau Élémentaire de l'Histoire Naturelle des Animaux," had 
divided two orders (one unnamed, the other Neuroptéres) into families 
* GILL, Johnson's Universal Cyclop:edia, new ed., III, p. 283, 1894. 
> The facts in the following brief résumé have been drawn chiefly from an address 
delivered by Dr. Theo. Gill before the Buffalo meeting of American Association for 
the Advancement of Science, Proc. A. A. A. S., XLV, p. 24 et seq., 1896. 
c Gill suggests that a happy mean may be obtained by adopting 13 divisions in the 
animal kingdom—branch and subbranch, and species and subspecies for the 
extremes—while the intermediate groups, order, family, and genus, are each accom- 
panied by a super and a sub group. 
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