Mammillaria heyderi ssp heyderi?

I posted the first two photos last May when I harvested chilitos. The plant never bloomed last year. The second two shots are current.









Here are the stats:
1 central spine, dark
16 radial spines, white/light cream
Ovoid-shaped chilitos
White/cream blooms with greenish-brown striping

I am thinking it has to be M. heyderi ssp heyderi, except for the glaring fact that is it quite globose - in no way it is flattened or did it flatten over the winter.

Experts, what do you think?

Regards,
Dustin
http://cactguy.tumblr.com

I'm pretty sure you are right in your identification of your plant as M. heyderi ssp heyderi. To be honest, I find separating some of the subspecies quite difficult, but the higher radial spine count does give support to ssp. heyderi.

It is described as flat-globose to globose, and really it depends on how much water it has. In winter, I'd expect it to flatten and draw down closer to the soil, and then when it has the first water, it will plump up. I think that is what you are probably seeing.