Palmer 1937 Peromyscus maniculatus 2 1/2 mi. S Antioch, 250 ft., Contra Costa Co., Calif. March 7. Caught 1 ? ad. in 24 gor. - size mouse traps. This one was taken at the top of a limestone outcrop on a low hill which was, for the most part, covered by by grass and annuals 1 1/2-2 inches high. The whole area was being heavily grazed by sheep. 1 mi. S Antioch, 100 ft., Contra Costa Co., Calif. Caught 1 in 40 gor.-size mouse traps. Taken in a runway (Microtus?) in grass - mixed green and dry - 6"-18" high along a roadside. The mouse had apparently come out of a small burrow just at the side of the runway. This burrow had a pile of fresh dirt at its entrance. A comparison of my 1 mouse with the numbers of caught by E.J. Hooper and D.T.D. Johnson in more open fields of young grain nearby may indicate a preference for the latter type of habitat here.