on low open hills of eroded exposures of gypseous, shaley Cretaceous limestone with Ariocarpus fissuratus, Stenandrium barbatum, Amsonia longiflora, Thymophylla acerosa, Xyloriza wrightii, Nama havardii, Polygala macrdenia, Nerisyrenia camporum, Anulocaulis leiosolenus,