1014" ME. OLDFIBLD THOMAS ON THE [Dec. 15,' 



that the labour and time demanded would have rendered the pre- 

 paration of the paper at all quite impossible, and partly because such 

 diagnoses can never be, really full and accurate unless prepared in 

 connection with the working out of the species of each genus. 

 Moreover, of all the groups he recognizes, Alston's paper contains 

 diagnoses, and it would be superiluous to repeat them here. 

 Where I differ from his conclusions full reasons are given iu the 

 footnotes. 



Comparing the numbers of recent families and genera recognized 

 in the two papers, we have 18 families in Alston against 21 now, 

 the difference being due to the Lophiomyidce being suppressed, and 

 the BatJiyergidce, Heteromyidce, Erethizontidce, and Pedetidce added. 

 Of genera Alston recognized 100, as against 159 now considered 

 valid ; of the additional 69 just about half are formed by the breaking 

 up of old genera and half are altogether new discoveries. 



Nomenclatural questions have of necessity ci'opped up here and 

 there, and the recent work of American authors in this respect 

 has been fully utilized. It is with the greatest regret that I have 

 had to use a good many names unfamiliar to English naturalists, 

 but the evidence in every case is so clear as to leave no room 

 for doubt, and none are mere matters of opinion. Eecognizing 

 that the ultimate use of these names is inevitable, J think the 

 sooner a knowledge of them is disseminated the sooner will the 

 intermediate stage of confusion be passed through and done with. 

 Where comparativel_y unfamiliar names are used, the better-known 

 terms are placed in brackets after them, as also are any special 

 synonyms which it seems of importance to mention. 



It should be again repeated that the special object of the list is 

 the proper allocation of the genera iu their respective subfamilies, 

 and I have purposely been as conservative as possible with regard 

 to the groups of higher rank, following Alston wherever there has 

 not been very special reason for departing from his arrangement. 



In regard, however, to Anomalunis and Aplodontia, both placed 

 by him in the Sciiu-omorpha, I have had to give in my adhesion to 

 the views expressed by more recent authors, that these two aberrant 

 genera cannot rightly be placed with the Squirrels. But where 

 they should go is by no means clear — Winge, Zittel, and Tullberg 

 all differing in the matter ; nor can I say that I agree with any 

 one of them. As it seems a pity to abolish the convenient and 

 time-honoured groups Sciuroinorpha, Myomorpha, and llyatrico- 

 morpha, just for the sake of these genera, 1 have thought it best 

 to put each of them under a special group-name ', leaving it for 

 further research to show their true relationships. Fortunately, 

 their serial position in the list, like that of Fedetes, may be left 

 almost exactly as in Alston's paper. 



' I have purposely not used names ending in morpha, as, apart from the 

 lenglli and clumsiness of the resulting combinations, I do not think it at present 

 advisable to consider the groups Anomaluri and AplodontiiU as of the same 

 rank as tlie Soiuromorpha and the others. 



