This is an Aspidocelis laredoensis. This is a parthenogenetic unisexual species that is a hybrid between gularis and sexlineatus. Identifying characteristics of laredoensis include the thin vertebral stripe, the bold reticulations on the upper surface of the rear legs, and the series of shield-like plates on the front of the forelimbs. Back in the good old days when I collected this, people were allowed in the area below the dam, but not anymore.