(Crotalus viridis viridis)
I know of prairie rattlesnakes from only three of the counties covered by this work - Culberson, Jeff Davis and Brewster (in the northern portions.)
I assume that they can also be found in Presidio County and perhaps Terrell County.
In Brewster county I have found them only by the Alpine airport, although I have had reports of them being found on Hwy. 118 south of Alpine. They are not a common snake within this range. They can easily be confused with diamondbacks or desert massasaugas. Notice that, although it has banding on the tail, it is not the black and white "coontail" found on the diamondback and mojave rattlesnakes. The rattles of the massasaugas is much smaller and pointed.