In their response to the comments by Thomas [1999], Davisson et al. [1999a] dismiss a large set of potentiometric measurements pertinent to an understanding of the hydrogeology of Yucca and Frenchman Flats in southcentral Nevada. This commentary is submitted to demonstrate, first, that their dismissal of this data set is unfounded and, second, that these potentiometric data call into question the central thesis of the original paper by Davisson et al. [1999b].