You searched for: Institution University of Michigan. Libraries Remove constraint Institution: University of Michigan. Libraries Place Vicinity of Cerro Zempoaltepetl, near Piksa'ah (Piedra Redonda) about eight kilometers east of summit, along trail to Zacatepec Mixes Remove constraint Place: Vicinity of Cerro Zempoaltepetl, near Piksa'ah (Piedra Redonda) about eight kilometers east of summit, along trail to Zacatepec Mixes Topic Usnea Remove constraint Topic: Usnea