For some years past it has been known that white-footed mice occur on the Anacapa group of the northern Channel Islands of California. In his Review of the Recent Mammal Fauna of California (Univ. Calif. Publ. Zool., vol. 40, no. 2, p. 175, Sept. 26. 1933), J. Grinnell referred the white-footed mouse of Anacapa Island, on the basis of probability as no specimens were available, to the race Peromyscus maniculatus santacruzae , described from Santa Cruz Island. Therefore, one of the primary objectives of the ninth Expedition of this survey was to secure a series of the Anacapa mice. Ample material was procured in August, 1940, and the results of the subsequent study indicate that the Anacapa form represents a recognizable geographic race, heretofore undescribed. It may be known and diagnosed as follows.