Mayhew 1958 Journal 104. Sept. 19 Colorado Desert, Calif. edge of some alfalfa fields. We stopped for the night at 2400. The air temp. was 31.5°C., road surface temp. was 32.5°C., & soil surface temp. was 29°C. Sept. 20 We started collecting at 0700 this morning. The first lizards were seen (Uta Stansburiana and Cnemidophorus tigris) at 0730. At this time the air temp. was 31.9°C., the soil surface temp. was 34°C, at this same time Mark & Fritz were capturing 3 young Phrynosoma micalli along the edge of the road. Eventually 2 more P. micalli were caught. By 0915, when we left for breakfast, the air temp. was 36.7°C., the soil surface temp. was 48.2°C. There was almost no reptile activity at this time (except for young Callisaurus draconoides). We returned to the same area at 1050, at which time we caught one Diplosaurus dorsalis sitting in the shade of Larrea divaricata. The air temp. waist high (the usual measuring location) was 39.2°C., air temp. 2 inches above ground was 43.5°C. The soil surface temp. was was 54°C. The Diplosaurus was caught without any chase, The cloacal temp. taken immediately upon capture was 43°C.,