Spread across a large section of central and southern South America (Peru, Argentina, Bolivia, Chile), Tunilla is a genus of 9 miniature cacti related to Opuntia. Segments can be flattened or cylindrical and are generally short making the plants low growing ground covers. Spination varies from short ghlochid like spines to much longer ones.
     This is a leggy cutting from Shoal Creek. I can't be sure of the ID as the stems are so thin.