llo. 39. 



NORTH AMEEICAN FAUNA. Nov. 15, 1915, 



REVISm OF THE POCKET GOPHERS OF THE 

 GEjN^US THOMOMYS. 



By Yerxox Bailey. 



mTRODUCTION. 



Pocket gophers, a group of rodents peculiar to North, and Middle 

 America, belong to the family Geom^ddge, which includes the genera 

 TJiomomys, Geomys, Pappogeomys, Cmtogeomys, PJatygeomys, Ortho- 

 geomys, Heterogeomys, Macrogeomys, and Zygogeomys. The present 

 revision deals only with the genus TJiomomys,^ which is distinguished 

 from the others by the practically ungrooved surface of the upper 

 incisors. The large fur-lined external cheek-pouches are a family 

 character shared by all genera and species, as are the general habits 

 of living in underground burrows and thro^vLD.g up heaps of earth 

 along their lines of tunnels. The genus TJiomomys includes 88 

 recognizable forms of 40 species. These vary in size from that of a 

 small mole ta that of a large rat, and in color from light buff to yellow 

 and gray, and from many shades of brown and rusty to dusky and 

 even black. All are short-legged, robust, stiu-dy little animals, 

 with small ears and eyes, and short, smooth hair. 



Gophers of the genus TJiomomys are abundant over almost the entire 

 western half of the United States, in a great area of southwestern 

 Canada, and over much of Mexico (see fig, 1), covering considerably 

 more territory than aU the other members of the family together. 

 The various forms do not overlap in range to any great extent, but 

 in the area occupied they are present in almost every locality, and 

 are especially abundant in fertile and valuable agricultural lands. 

 Their burrows are a constant menace to agricultural operations, irri- 

 gation ditches, and reservoirs. Their food is entirely of vegetable 

 matter, and of this roots, bulbs, and cultivated crops are preferred. 

 In destroying crops and fruit trees 'they cause a heavy loss to western 



iln 1895 Dr. C. Hart Merriam monograplied the family Geomyidse, exclusive of the genus Thomomys 

 (N. Am. Fauna Xo. 8), and also included a chapter on the anatomy and relationships of Thomomys and a 

 map of the genus without reference to its specific and subspeciac divisions. It was my privilege to assist 

 him in working over the material for his monographic revision and later I was assigned the task of com- 

 pleting the revision of the genus TJiomomys. 



7 



