J. Chatti Microdipodops megacephalus July 31 N.E. edge Alkali lake, 4200ft., Lake Co., Oregon Caught 2 ? specimens in drifted sand near greasewood brush. Soil is soft and sandy. Vegetation surround is greasewood with some sagebrush. Mice were caught about 50 yds West of N.E. edge of the dry lake bed of Alkali Lake. Burrows fairly abundant in vicinity resembling those of Perognathus. Tail marks inferred to be those of Microdipodops are about 2-4 in. long and fairly thick (wide). In comparison they are wider than the tail mark of Perognathus farvus and shorter but of about the same width as those made by Dipodomys cordii.