Notocactus magnificus, also known as parodia magnificus, is native to Brazil and Uruguay. This cactus is easy to grow and will bloom several times during warm weather. Even though in its native habitat it can withstand lots of daytime heat and cold weather at night, if you have extended cold or freezing weather, I would suggest you treat as not cold hardy.
All of my notocactus magnificus specimens have the yellow spines and green bodies, but I have seen some with grayer bodies and silver spines. I think they also produce yellow flowers.
All notocctus magnificus have a nice round ball-shaped body, or at least they start out that way. As you can see here, the older one in the dish garden behind the one in bloom has grown tall. The first one I had grew so tall that it became top-heavy and leaned over the side of the pot and was awkward, so I sliced off the top about 3 or 4 inches from the base. It responded by making a cluster of crowns all around the rim of the cut part of the plant and grew into a lovely clump of cactus. And I took the severed top, trimmed the remaining crown up into the less woody part of the body and rooted it. I sold both parts and started over with younger plants. It will be interesting to see if this taller one winds up falling over, too. And if it does, I will most likely operate on it as well.
But one way or the other, I will always have at least one of these rewarding cactus in my collection.