170 Proceedings of the Biological Society of Washington. 



Remarks. — The pocket gophers of the isolated prairies of western Wash- 

 ington show the effects of segregation. Broadly speaking, one may say that 

 those inhabiting each prairie represent a local variant. While the charac- 

 terization of each of these would be confusing, the recognition of the more 

 obvious forms is desirable. Thomomys douglasii douglasii is one of these, 

 T. d. yelmensis another, and T. d. tacomensis a third. Specimens from 

 localities between the type locality of the present subspecies and that of 

 yelmensis are of somewhat intermediate character, and might be referred to 

 either subspecies, according to specimens now in hand. Their precise 

 allocation must await the acquisition of additional material. 



Specimens examined. — Total number 16, as follows: 



Tacoma (6 miles south), Pierce County, 8; Steilacoom, Pierce County, 

 2; Olympia (4 miles south), Thurston County, 6. 



