44 



although so much has been done during the last five years, 

 the published results form but a beginning toward a proper 

 knowledge of the mammalian fauna of North America. 



Thus far in this paper reference has been made mainly 

 to the discovery of new forms as evidence of the recent 

 advances in our knowledge of North American mammals, 

 and little in respect to increase in knowledge along other 

 lines, or of particular geographical areas. Most of the new 

 forms have of course come from the little known parts of 

 the West, and from countries south of the United States, 

 where collecting had been exceedingly superficial and 

 sporadic, the material previously gathered being such as 

 chance threw in the way of comparatively untrained col- 

 lectors. Less than a decade ago the more unsettled parts 

 of the West, and especially the extensive arid regions, 

 were practically virgin ground, so far as the systematic 

 trapping of small mammals was concerned. Now there 

 are few areas of any great extent that have not been visited 

 by trained collectors with the best modern devises for 

 capturing small mammals; while considerable portions of 

 the country have been methodically explored, with a view 

 not merely to securing large series of specimens from 

 certain selected localities for comparative study, but 

 especially for the purpose of determining the geographical 

 distribution of particular forms or groups of forms, as 

 regards both their vertical and horizontal range. In the 

 western and southwestern portions of the United States 

 many thousands of square miles have been systematically 

 surveyed biologically under the direction of Dr. C. Hart 

 Merriam, 1 Chief of the Division of Ornithology and Mam- 

 malogy, United States Department of Agriculture, who for 

 the last five years has been able to keep in the field a 

 large corps of skilled collectors. Under the same auspices 

 much collecting has been done also in the East and South, 



1 See N Am. Fauna, Nos. 3, 4, 5 and 7, for reports on his explorations in Arizona, 

 Idaho, and southwestern California and contiguous regions. 



