Baird, S. F. 1859. Report upon the reptiles of the route. Reports of Explorations and Surveys to Ascertain the Most Practicable .... Route for a Railroad from the Mississippi River to the Pacific Ocean. Route Near the Thirty-fifth Parallel, Explored by Lieutenant A. W. Whipple ... Assisted by J. C. Ives. Volume 10, Part 6 (Zool. Rep.), Number 4: 37–45, pls. 25–27. Washington, D.C.