Mammillaria heyderi ssp?

Does anyone know which M. heyderi this is? It was found in Denton County, Texas.







Thanks for your help,
Dustin
http://cactguy.tumblr.com

Heelo Dustin
Might be Escobaria

Hi Dustin,

If you look closely (certainly at the plant in your first photo), you can see a grove on the upper side of the tubercle. That would mean that it isn't a Mammillaria, but either a Coryphantha or Escobaria.
I think that this is Escobaria missouriensis, though I haven't heard of a population in Denton Co., the area from which is has been most frequently reported is Lafayette Co, se of Austin. But it is a widely distributed species, though not as widely as EScobaria vivipara, so I think my identification is likely to be right.

Thanks, Chris. The individual who found the colony is pretty confident someone had placed the mother plant there, so it could certainly be E. missouriensis. Thanks for your help.