A LIST OF THE GENERA AND FAMILIES OF MAMMALS. 21 
The first two methods date back to the * Stricklandian Code’ of 1842, 
known also as the ‘Rules of the British Association. Both have been 
generally advocated and more or less generally followed, but both are 
beset by serious objections. The simple rule of adopting the first 
species as the type fails signally when applied to Linnean genera, some 
of which seem to have their types concealed in the middle of a list of 
species. Thus the type of J/vstel~ would become .M. /utris, the sea 
otter; of Mus, M. porcellus, the guinea pig; and of Cervus, C. camelo- 
pardalis, the giraffe. The adoption of the verdict of the first reviser 
is open to the objection of leaving too much to personal opinion in 
determining what constitutes revision (monographing the group or 
merely enumerating the species). Moreover, there is always the diffi- 
culty of actually determining which author was really the first to revise 
the group, and if the one whose verdict has been generally accepted 
proves to have been anticipated by another of different views, change 
and consequent shifting of names are inevitable. 
"The third method was advocated by Prof. Alfred Newton" about 
thirty years ago and has recently been adopted by a number of Ameri- 
can zoologists, as a rule, in the following form: ‘‘A generic name 
which is the same as that of an, explicitly included species (or a cited 
post-Linnean synonym of such species) takes that species as its type 
regardless of subsequent elimination." This method is open to no 
serious objection and disposes satisfactorily of a certain class of cases 
which, however, are rather limited in number. 
The fourth method, that of elimination, is applicable when others 
fail, but should be used with the restrictions provided by Canon XXIII 
of the A. O. U. Code (p. 43). "If, however, the genus contains both 
exotic and non-exotie species—from the standpoint of the original 
author—and the generic term is one originally applied by the ancient 
Greeks or Romans, the process of elimination 1s to be restricted to the 
non-exotic species.” 
Recently Dr. Jordan,’ in discussing the determination of types, rec- 
ognized three general methods: Following the arrangement of the 
original author, elimination, accepting the type designated as such by 
the original author. In the last case the question is very simple, as the 
statement can not be reversed by any subsequent writer. If no type 
is designated he favors adopting the first species as such, with certain 
exceptions. The five principles which he has formulated for guidance 
in determining types are as follows: (1) The species designated as 

«Newton in Yarrell’s Hist. Brit. Birds, 4th ed., I, p. 150, 1871; Ibis, 3d ser., VI, 
pp. 94-104, 1876. See also note in Coues's Bibliog. Ornith., Bull. U. S. Geol. Surv. 
Terr., V, p. 751, 1879. 
bSee Science, new ser., XVI, pp. 114-115, July 18, 1902, 
v 'The Determination of the Type in Composite Genera of Animals and Plants,’ 
Science, new ser., XIII, pp. 498-501, March 29, 1901. See also a still more recent 
article on ‘The Types of Linnean Genera,’ Ibid., XVII, pp. 627-628, Apr. 17, 1903. 
