R. Zweifel 1953 Journal En route north from Mazatlan, Sinaloa July 19 238.0 Leave camp 11:00 AM 266.13 RR track 269.2 cross road to Las Machias 280.0 Rio Fuerte - leave flat coastal plain and enter hills for a few miles. 302.13 Caled road 312.8 Continuous pavement reached. Of the intervening 147 miles, there are some short stretches of pavement and large regions where highway normal speeds are possible over a good dirt surface. However, there are still many miles where the rocky surface necessitates speeds not over 15-20 mph. 370.4 Navojoa (Sonora) 413.6 Ciudad Obregon 418.2 Dinner stop. Cnemidophorus tigris, Dipsosaurus dorsalis, sceloporus magister, Bufo cognatus. The toad involves a range extension of some 350 miles to the south. Doesnt vegetation, not thick enough to be termed thorn forest. 419.9 Rana pipiens and Pteromylula fordina found in a roadside saw pool. The single Pteromylula was seen calling, but escaped.