mammillaria....

a plant flowered for the first time, to which i can not give a name.....
there are a lot of bristles in the axils.

It looks like Mammillaria albata to me. I believe M. albata is distinct than M. leucocentra in which it is placed as a synonym.

I agree with you, Amante, it does look like M. albata.

I have always had my doubts about the assignment of M. albata to M. leucocentra. One reason is that I am by no means sure that leucocentra is a good subspecies. Across the range of M. geminispina one finds plants with varying characteristics. I have seen plants near Venados that match the description of leucocentra, though it is supposed to be found more to the west.

To separate out a subspecies from a highly variable species just because of spine length and colour seems to me to be a step to far. If one wants to do this, then you have to be consistent and apply the same rule to other species. This would cause many problems, I believe. The plants designated as M. geminispina ssp. leucocentra are not geographically separated, and are just one form of the highly variable M. geminispina, which can be found throughout the distribution.

So, if one lumps albata to leucocentra, one should lump leucocentra to geminispina and just have one broad highly variable species. After all that is what Hunt and others have done to M. magimamma!