From Rio Grande do Sul, Brazil, Parodia scopa ssp. succinea is a sometimes clumping globular cactus to 3 inches across. It is virtually indistinguishable form Parodia scopa ssp. scopa until it flowers. Parodia scopa ssp. scopa flowers have red stamens wheres ssp. succinea are entirely yellow.
     I got this from a sale at Tucson Botanical Gardens labled Notocactus succineas. I wasn't surprised it was a subspecies of P. scopa. The flower pics were taken in late April.

Flowering in April

Closeup of flowers