24 



Carnivores. In other words, the larger and diurnal species, 

 as the Deer and larger Carnivores, were relatively better 

 known in 1884 than the smaller species that burrow in the 

 ground and are for the most part abroad only at night. 



These statistics, however, very inadequately express the 

 results of the work of the last decade, — or more correctly 

 of the last seven years, for little advance was made prior 

 to 1887. Since this date have been made not only the ad- 

 ditions and other changes indicated above, but many 

 radical changes in the nomenclature of species have been 

 found necessary, in consequence of the former misappli- 

 cation of names. Also many forms formerly ranked as 

 subspecies have been found to be entitled to specific rank ; 

 many names that had been reduced to synonyms have been 

 revived for forms which prove to be tenable as subspecies, 

 and to which they were evidently intended to apply, though 

 originally very inadequately characterized. Again, forms 

 originally characterized as species, and known only from 

 limited areas and few specimens, have proved separable 

 into several well-marked subspecies, and in some instances 

 into species, and their known geographic range greatly 

 extended. 



In order to emphasize some of these points it will be 

 necessary to pass in review a few special groups. Although 

 little monographic work has as yet been attempted, owing 

 to lack of material and time for final revisionary work, yet 

 the results that have been reached in the few instances in 

 which such work has been undertaken have stood the test 

 of re-examination much better than might have been ex- 

 pected. It is almost too soon yet for final work in any 

 group, but we may hope to reach the point ere long when 

 the material will be sufficiently abundant to warrant the 

 attempt, in the case at least of some of the better known 

 generic groups. 



The following genera will be taken in illustration of the 

 subject : Lepns, Heteromy s , P erognatlius , Dipodomys, Pero- 

 dipus, Thomomys, Geomys, Phenacomys, Evotomys, Synap- 



