29 . 



12 species and 6 subspecies in the former, and g species and 

 2 subspecies in the latter, or a total increase of from 2 to 29 

 forms, with a considerable extension of the known range 

 of the group. Besides these additions, an allied genus 

 Microdipodops has been described from Halleck, Nevada, 1 

 which combines the external characters of some of the 

 species of Perognathits with many of the cranial characters 

 of Perodipus. 



The Pocket Gophers form a group of burrowing Rodents, 

 restricted to North America, and constituting two strongly 

 marked genera, Thomemys and Geomys. They live almost 

 wholly underground, and can be secured only by trapping 

 them in their burrows. In Mr. True's List Thomomys is 

 credited with two species (one of them then known only 

 from the type specimen) and two additional subspecies. 

 This genus has now 16 species and 1 subspecies, 2 and its 



Perodipus richardsoni (Allen), Bull. Am. Mus. Nat. Hist., Ill, p. 277. 

 Oklahoma Territory. 



Perodipus sennetti (Allen), ibid., p. 226, April, 1891. Cameron Co., Texas. 

 Perodipus compactus (True), Proc. U. S. Nat. Mus., XI., p. 160. Jan. 5, 



1889. Padre Island, Texas. 



Perodipus chapmani (Mearns), Bull. Am. Mus. Nat. Hist., II., p. 291., Feb., 



1890. Fort Verde, Arizona. 



Perodipus longipes (Mernam), N. Am. Fauna, No. 3, p. 71, Sept., 1890. 

 Painted Desert, Arizona. 



1 Merriam, N. Am. Fauna, No. 5, p. 115, July 30, 1891. Type, M. mega- 

 cephalus, sp. nov. 



- For a recent preliminary revision of the genus see Allen, Bull. Am. Mus. 

 Nat. Hist., V., 1893, pp. 47-68. On T. bulbivorus see an important paper 

 by Gerrit S. Miller, Jr., Proc. Biol. Soc. Wash., VIII., pp. 113-116., Aug., 

 1S93. 



Following is a list of the United States species : 



Thomomys bulbivorus (Rich.). Thomomys clusius Coues. 



Thomomys laticeps Baird. Thomomys talpoides (Rich.). 



Thomomys bottce (Eyd. and Gerv ). Thomomys fulvus (Woodh.). 



Thomoviys townsendii (Rich.). Thomomys perpallidus Merr. 



Thomomys monticolus Allen. Thomomys aureus Allen. 



Thomomys douglasii (Rich.). Thomomys fossor Allen. 



Thomomys douglasii fuscus (Merr.). Thomomys toltecus Allen. 



