The first thing that doesn't look right is the flower colour. All perbellas that I have seen have carmine flowers, and tend to be tighter in appearance, though that could be cultural. However I wouldn't have thought Texas was short of good sunlight!
The central spines don't look right, though they are right in number, but perbella's centrals are usually much stubbier, thicker at the base, and much shorter.
What immediately went through my mind was that this might be a form of M. formosa, which is a very variable species. If you look through the A-Z gallery, under M. formosa you will see the vast range of variation, and your plant bears quite a bit of resemblance to the one with the Rog 326 field number, though it snot exactly the same.
Without knowing where the original collected plant came from, and indeed assuming it has been bred true, it is difficult for me to be more accurate. Hopefully others might have better thoughts?