Silver Ball Cactus
There are a bunch of subspecies of this little yellow-flowered plant. I don’t know which one this is, but we’ve also had some with white spines.
So for the past few days I’ve been mentioning how natural variation is a good thing, and we don’t need to give all variants their own cultivar names. But in this case there are more differences, so one would use the subspecies designation. If I knew which one this was, I would use the ssp. name. That’s just common sense, in a botanical sort of way.