10 September 1958.
Zacatecas, Mexico
Locality: 20 miles from Fresnillo on the road to Durango, Valuarte. At the base of a small hill, 0.5 km W of the main road, near the resevoir.
Coordinates: 23.1667, -102.8833
(Map it)
Elevation: 2150m.
Environment description: Under Opuntias and Prosopis.