Bailey Identity of Thomomys umbrinus (Richardson). 5 



SKULLS OF Thomomys fulvus and umbrinus. ALL NATURAL SIZE. 

 No. 32,058 Thomomys fulvus from Springerville, Arizona. 



No. 1,122 Thomomys umbrinus. Photograph of type specimen in British Museum. 

 Nos. 64,091 and 64,092 Thomomys umbrinus from Boca del Monte, Vera Cruz, Mexico. 



