1896.) GENERA OF RODENS. 1013 
Now, every Museum-curator when arranging his specimens, and 
every writer either of a text-book or of ‘a faunistic work, is con- 
stantly being confronted by the difficulty as to where to place in 
the system this or that genus of Rodents, for which he has perhaps 
himself neither time, inclination, or opportunity to search out a 
proper andappropriate position. It is for the object of helping such 
persons that the present paper has been prepared, so bold a venture 
being due to the fact that the increase in the British Museum collec- 
tions has fully kept pace with the general increase of knowledge, and 
that there are very few genera known from any part of the world of 
which specimens are not in that collection’. With such unrivalled 
material available, the opportunities for mistaken work have been 
reduced to a minimum; and in the following list it may be said that 
the specimens have been allowed to sort themselves, and where 
my alterations are found to be strikingly different from those of 
Alston it will generally be found that the forms referred to were 
not available for examination in his time *. 
One recent author only has diverged much from Alston’s system, 
namely Dr. Winge of Copenhagen, who, in connection with his 
work * on the Rodents of Lagoa Santa in Brazil, has written a 
revised general arrangement of the Rodents. His classification, 
however, is a rather one-sided one, being based almost entirely on 
the structure of the masseter muscles and the bones related to them, 
and, however thoughtful and clever it may be in many ways, is so 
widely divergent from all previous classifications that without much 
stronger reasons than he adduces I should not be prepared to 
follow it. No doubt many of his alterations are admirable, such, 
for example, as the reference of Sminthus to the Dipodide ; but 
when we find Pedetes placed with Anomalurus, and Platacanthomys 
combined with Myowus in a group set over against Graphiurus, 
we see that a good deal of confirmation will be needed before the 
classification the world is accustomed to is abandoned in favour of 
that proposed by Dr. Winge. Prof. Zittel* and Dr. Tullberg ?’ 
have also contributed to the revision of the classification of the 
Rodeuts. The former gets rid of the difficulties by putting all the 
awkward families into a separate group, the Protrogomorpha. The 
latter largely follows Winge, but does not as yet enter into details. 
Dr. Trouessart’s most useful list of Rodents is entirely based on 
Alston’s arrangement, and is so admittedly a compilation that no 
special criticism of it is here necessary. 
No attempt has been made to follow Alston’s example of giving 
diagnoses of the groups and genera, partly for the simple reason 
* Handb. Paleontol. p. 512 (1893). 
® Muriden aus Kamerun (Nova Acta Soc. Upsala), sec. 3, xvi. p. 4 (1893), 
