1896.] GENERA OF KODHHTl'S. 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 and appropriate 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 Eodents of Lagoa Santa in Brazil, has written a 

 revised general arrangement of the Kodents. His classification, 

 however, is a rather one-sided one, being based almost entirely on 

 the structure of the masse ter 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 exam])le, as the reference of Smintlms to the Dipodidce ; but 

 when we find Pedetes placed with Anomalurvs, and Plaiacanthomys 

 combined with Myo.nis 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 

 Eodents. The former gets rid of thedifiiculties 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 Eodents 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 



' Of the 159 genera now aclniittecl, only the following 16 are not represented 

 in tlie Museum collection : Idinrvs, Orewomr/s, Bcomys, Liviaccmivs, IHiheco- 

 ckirus, Hallomys, Hypogcomys, Notimnys, Xe^wmys, Microdipodops, Eiwhoreuies, 

 Massouiiera, Cercomys, Dinomys, and 'liomerolagus. 



^ E. g., Heterocephalus, Lophuromys, Stcatomys, Saccostomtis, &c. 



' Jordf undne og nulevende GnaTere fra Lagoa Santa, E Mus. Lundii, iii. 1887. 



* Handb. Patoontol. p. 512 (1893). 



' Muriden aua Kamerun (Nova Acta Soc. Uppola), Bee. 3, xvi. p. 4 (1893), 



