A LIST OF THE GENERA AND FAMILIES OF MAMMALS. 13 
REFERENCES AND DATES. 
REFERENCES. 
Great care has been taken to ascertain the original place of publica- 
tion of every genus. This apparently simple object is often difficult 
of attainment, owing to the obscure manner in which some names are 
published and the practical impossibility of determining whether or 
not the reference found is really the first. The matter is important, 
since a difference of a few months or even a few days may decide the 
availability of a name." A difference in publication of one year caused 
the rejection of such well-known names as Arvicola, [somys, and 
Ochetodon, while priority of only three days resulted in the adoption 
of Matschie's Zenkerella in place of De Winton's Aethurus, in 1898. 
Hipposideros Gray is sometimes quoted 1834 (Proc. Zool. Soc. Lon- 
don, p. 53), where it is a nomen nudum, while reference to the original 
description in 1831 (Zool. Miscellany, p. 37) shows it to be a valid name. 
Oreas Desmarest is usually quoted 1822, and if correctly so it is pre- 
occupied by a genus of Lepidoptera (1806) and by a genus of Polyps 
(1808). It is, however, said to have been described in 1804, and should 
this prove to be a fact the name would supplant Zawrotraqus, which is 
now adopted for the group. 
Different species are also likely to be enumerated in later references, 
and the supposed type derived from a reference commonly accepted 
as the earliest may prove to be different from the actual type as shown 
by the original description. Transference of type may be illustrated 
by the different editions of Linneus: In the tenth edition, 1758, J/anzs 
contains only one species, JM. pentadactyla, which is necessarily the 
type; in the twelfth edition, 1766, two species are given, JV. penta- 
dactyla and M. tetradactyla, and the latter has recently been given as 
the type of the genus. (W. L. Sclater, Mamm. S. Africa, II, p. 216, 
1901.) 
Secondary references have been freely admitted to indicate the sev- 
eral publications in which a name appeared at close intervals, to indi- 
cate changes in spelling, to call attention to important monographs or 
revisions of groups, to show when subgenera were raised to generic 
rank, and to fix responsibility for determination of types. No 
attempt, however, has been made to include every important second- 
ary reference, and more citations will be found under some names 
than under others. The reason is evident, for while well-known 
generic names may be found in almost any book of reference, some of 

.* A few years ago Oldfield Thomas, supposing that Cuvier's well-known genus 
Cricetus dated from the * Régne Animal, 1817, proposed to replace it by Hamster 
Lacépéde, 1799 (Proc. Zool. Soc. London, 1896, 1019). The name, however, was 
used by Kerr in 1792, and in reality has seven years’ priority over Hamster. 
