R. Zweifel 1953 Crotalus molossus 7 mi SW El Vergo (Zagunta) 7800', Chihuahua, Mexico 2341 RZ July 3 While hunting Eleutherodactylus on a rocky outcrop after dark, a rattler was found crawling slowly over the rocks only about thus far from where the frog was calling. The rocks were dry, although the ground was damp from the showers of the afternoon and early evening. The air temperature at camp was 60° F a few minutes after the snake was captured, and probably close to that at the site of capture. The snake felt cold to the touch. General coloration brown, tending toward olive on the sides. Diamonds yellow. There is a very faint indication of rings on the tail beneath the black.