Identificaciones de gonzalezii

Was clearing an area of thorny scrub on a limestone shelf above the river--found and transplanted several multi-headed clumps of this small cactus--Mammillaria prolifera. I've only ever found it in well-shaded locations under thick vegetation. This would be M. prolifera var. texana, but the variety doesn't seem to be an option here. This variety is also called the "Texas pincushion".

This is the nominate variety of Texas Paloverde, formerly placed in the genus Cercidium. It is a shrubby form of the larger, tree-form P. texana var. macra (formerly Cercidium macrum). It has a limited distribution in desert scrub in Southwestern Texas. (Note that there is only one pair of pinnae on the single leaf that I photographed--a distinguishing character.)
http://plants.usda.gov/core/profile?symbol=PATET2
http://bonap.net/MapGallery/County/Parkinsonia%20texana.png