1915.] INTRODUCTION. 19 



progress over the animal along a semicircular line. The line is not 

 so conspicuous, however, as the longer hair overlaps the short summer 

 coat which it is crowding out, and does not exhibit the plumbeous 

 color along its margin. Often before the first coat has reached the 



B2044-122 



Fig. 3. — Skins of Thomomys (U. S. Nat. Mus. specimens) showing waves of pelage during molt. 



1. Thomomys talpoides rufescens. male adult, No. 180486, Valley City, N. Dak., May 17, 1912, showing 



five waves of pelage during spring molt. 



2. Thomomys quadratus fisheri, male adult, No. 94411, Ruby Valley, Nev., June 23, 1898, showing four 



waves of pelage during spring molt. 



3. Thomomys talpoides clusius, female adult, No. 160396, Shirley Mountains, Wyo. (8,800 feet altitude) 



Aug. 21, 1909, showing three waves of spring molt, with coat of previous winter on rump and two 

 waves of fall molt coming in on head: two winter coats at one time. 



4. Thomomys quadratus fisheri, male adult, No. 80721, Cottonwood Range, Nev., Sept. 17, 1896, show- 



ing first wave of fall molt back to rump, second wave back to ears. 



base of the tail the second has begun on the nose and is following the 

 first (fig. 3). This seems not to replace the first but to fill up and 

 thicken the coat, while both may increase in length as the weather 

 becomes more severe. 



