761 Thomomys monticola (1) Horse Mt., 4700-5200 ft., Humboldt Co., Calif. June 5, 1933 Numerous working on crest & bare knurkles on ridge east near Cold Springs. The great majority of the workings are winter cores but there are a few scattered surface mounds of recent date. No. 2747 - had 4 pairs mammae 2 abdominal - 2 phaenic (essentially in two sets). Taken by Belle at about 400 ft alt., on dry hillside. Evidently T. bottae & T. monticola intermingle but do not interbreed June 7, 1933 Spec. 2749 & 2750 were taken on grassy barren knolls on crest ridge. One was trapped in a burrow mouth scarcely marked by a mound & the other at a fresh mound which was indistinguishable by me from mere mounds near key. No. 2749 was taken in small opening in heavy timber about 150 yds from bare crest ridge. Only one mound area had been erected in this clearing.