Glad that you managed to work through the image posting stuff, it can be a bit daunting the first time.
Your plant is, I believe, a form of Mammillaria formosa. This is a very variable species, and if you look at the A-Z gallery under F, and then formosa, a long way down the many photos you will find a photo of M. Formosa aff Rog 326. This form has close white radial spines and an upward pointing very short dark central spine. Your plant resembles this, though I can't be sure it is exactly the same, but certainly the same species.