PART III.—INDEX OF GENERA ARRANGED ACCORDING TO 
ORDERS AND FAMILIES. 
INTRODUCTION. 
The alphabetical indexes of genera and families in Parts I and II 
will facilitate reference to a given name and aid in ascertaining its 
place of publieation, its type, or its etymology; but if it is neces- 
sary to know what names have been used in a certain group, why a 
name is unavailable, or whether any published name is available for 
one which is preoccupied, such information can be obtained from them, 
if at all, only after much labor, or by first consulting elsewhere a full 
list of synonyms of the group. 
These difficulties became apparent early in the progress of the work, 
and in order to obviate them experiments were made in tabulating the 
names under each of the higher groups. The most satisfactory 
arrangement was published in December, 1897, in a paper entitled 
‘A List of the Generic and Family Names of Rodents.’“ In this list 
the names were arranged alphabetically under families, and the recent 
and extinct groups distinguished by the use of black-face type for the 
former and italics for the latter, as in the following pages. Every- 
thing was subordinated to convenience of reference; genera and sub- 
genera were treated alike, references omitted, and the accompanying 
data reduced to the three most important items of author, date, and 
type or included species, so that the entries under each name would 
be as brief as possible and in ordinary cases restricted to a single 
line. 
This arrangement seemed to serve the purpose so well that it has 
been adopted in the present work with three important modifications— 
addition of the type localities (which, however, are usually reduced to 
two or three words), incorporation of cross references to direct atten- 
tion to synonyms or new names for those preoccupied, and omission 
of variants except those which differ in the initial letter or are other- 
wise of special importance. 
ARRANGEMENT. 
As in the other parts of the work, orders, families, and genera are 
alphabetically arranged. But this has made it difficult in some 


€ Proc. Biol. Soc. Wash., XI, pp. 241-270, 1897. 
