14 INDEX GENERUM MAMMALIUM. 
the obscure ones are extremely difficult to find, and hence it is desir- 
able to bring together the more important facts in the history of 
names published in works which are not generally accessible. 
The references are brief, but at the same time full enough to indi- 
cate clearly the book or paper (without confusing titles of similar but 
distinct works), the edition, volume, page, plate, and figure where the 
name may be found. As a rule the inclusive pagination is given 
instead of the first page or the one on which the generic name appears, 
in order to indicate to some extent the length of the description and 
thus give a clue to the detail with which the group is treated. 
Nearly every reference has been verified, and in the majority of 
cases checked independently by two persons, so as to eliminate as far 
as possible errors due to copying. It is difficult to appreciate the 
time, labor, and energy expended to secure accuracy in this respect. 
Special trips have been made to libraries in distant cities in this 
country,and my assistant has visited the principal libraries in Bergen, 
Berlin, London, and Paris in the quest for rare books. Still, in a few 
instances, it has been necessary to take references to inaccessible works 
at second hand, but these are quoted or accompanied by a statement 
of the authority from which they have been derived. 
DATES. 
The determination of the date of publication is one of the most 
important points connected with nomenclature, as it is the foundation 
of all matters respecting priority of names. Ina technical sense the 
publication of a book or paper is distinct from the date of printing 
and practically synonymous with distribution.” Publication is defined 
by the Century Dictionary as ** The act of offering a book, map, print, 
piece of music, or the like, to the publie by sale or by gratuitous 
distribution." According to the late Dr. Coues, ** A printed work is 
‘published’ if a single copy is placed in a publie library.”? Although 
it is a general rule that the date of publication is to be accepted unless 
there is evidence to show that it is incorrect, yet it must be remem- 
bered that many scientific papers, particularly monographs and elabo- 
rate works, are published in parts, and when these parts are gathered 
in volumes the date on the title page is, in most cases, simply that of 
the last brochure. Such publications, therefore, have both a real and 
an apparent date—the real date being the time of publication of the 
separate parts; the apparent date that on the title page. These two 
dates may vary several months or even years, as in the case of the 
‘Proceedings of the U. S. National Museum,’ ‘Proceedings of the 
Zoological Society of London’ for 1850, or the ‘Transactions of the 
Zoological Society of London.’ An extreme case is that of Pallas’ 
a@See Allen, ‘Science,’ N. S., IV, 691, 838, 1896. 
^ Coues, in Allen’s Mon. N. Am. Pinnipeds, p. 254, footnote, 1880. 
