1914.] 



INTRODUCTION. 



9 



and the range of the genus was shown to extend practically across 

 the continent from the Carolinas to California and south to Costa 

 Rica. Of the 15 forms recognized; three {nebrascensis, deserti, and 

 pallidus) are considered synonjans by the present writer. Dr. 

 Allen's material consisted of 920 specimens, chiefly from the United 

 States. The paucity of material from southern Mexico, where the 

 genus reaches its highest development, of course accounts for the 

 incompleteness of this revision in so far as the southern forms are 

 concerned. Only 2 specimens from southern Mexico and 17 from 

 Costa Kica .were at that time available — only 19 specimens from a 

 region where over 35 subspecies are now known. 



As a result of increased activity in the collection and study of 

 North American mammals, new species were discovered almost 

 every year. In 1898 Thomas described R, soderstromi from Ecuador, 

 thus extending the range of the genus into South America. In 1901 

 Merriam published a paper ^ giving descriptions of 23 new forms, 

 based chiefly on the unexampled collections of Nelson and Goldman 

 in Mexico and Guatemala. Since that date 9 additional species 

 have been described, bringing the total number of named forms up 

 to 67, of which 16 are at present regarded as synonyms. Fifty-eight 

 forms are recognized in the present revision, of which 7 are here 

 described as new. 



The material on which the present revision is based consists of 

 2,280 specimens contained in the collections of the United States 

 National Museum, including that of the Biological Survey, and the 

 Merriam Collection. This material has been supplemented by a con- 

 siderable number of specimens borrowed from other American muse- 

 ums, thus bringing the total number of specimens examined up to 

 2,583. All the existing types have been examined with the excep- 

 tion of R. tenuis, R. soderstromi, and R. modestus, which are in the 

 British Museum, and R. mexicanus and R. sumichrasti, which are in 

 the Geneva Museum. Of the last two I have seen photographs of 

 the type skulls, while of tenuis and modestus I have examined prac- 

 tical topotypes. The National Museum collections contain repre- 

 sentatives of all but 5 or 6 of the recognized forms and in most cases 

 considerable series showing all ages and pelages. 



In this connection I wish to acknowledge the kindness of the fol- 

 lowing gentlemen, who have generously loaned from the collections 

 under their charge such material as was needed to supplement the 

 collections in the National Museum: Dr. J. A. Allen, of the Ameri- 

 can Museum of Natural History ; Mr. Outram Bangs, of the Museum 

 of Comparative Zoology; Mr. F. J. V. Skifi, of the Field Museum of 

 Natural History; Mr. Witmer Stone, of the Academy of Natural Sci- 



1 Proc. Wash. Acad. Sci., in, 1901, pp. 547-558. 



