Paris 1946 Pipilo fuscus 47. Guadalajara, Jalisco, Mex. to San Luis Potosi, San Luis Potosi, Mex. Aug. 7, 1946 definitely arid. A P. fuscus taken 4 mi. SW of San Juan de los Lagos has pale undercoverts and an almost white Gular patch, although the dorsal color- ation seems darker than specimens taken around Cerote, Vera Cruz, Mex. The coun- try becomes progressively more arid to desert-like farther NE. There are great, dense stands of Saguaro cactus, some barrel and colla cactus, and scattered xerophy-ti thorn scrub. In short, we have a meteor- ological cline of increasing aridity from SW to NE, and an accompanying clinal change in the Brown Towhees, the birds increasing in size and pallidness. The country from the city of San Luis Potosi to a point about 15 mi S W is utterly barren desert, mostly rocky hills without vege- tation, a real "Stone Orchard". Brown Towhees were seen commonly all the waysave for the stony hills where there was not enough scrub growth to support them. Potosinus appa- rently represents a clinal extreme rather than an isolated subspecies. There is undoubtedly a long, gradual clinal change from Guada-