13 October 1983.
San Luis Potosí, Mexico
Locality: Sierra de Catorce, road turning off 10 km west of Cedral (north of Matehuala), track to real de Catorce, 2 km above tunnel.
Coordinates: 23.6900, -100.8900
(Map it)
Elevation: 2740m.
Environment description: Border of maize field, on path among stones.