From the states of Oaxaca and Puebla, Mexico, Coryphantha retusa is a normally clumping globular cactus to 4 inches across. It produces pale yellow flowers with reddish centers in late summer and fall.
     This was from Bachs and looks very similar to my C. cornifera. It has the same curved central spine. It's allready more than 4 inches across (that's a gallon pot its in) and showing no signs of producing offsets. Si'm not sure on the ID. I guess I'll leave it as marked for now and wait on a flower.