The present paper is the third and last of the series of reports on the herpetological results of the University of Illinois expedition into northeastern Mexico in the spring of 1949. During the twenty day period from April 13 to May 1, 258 specimens of lizard were obtained in the Mexican states of Hidalgo, Nuevo Le6n, Puebla, San Luis Potosi, Tamaulipas, and Veracruz and in southern Texas. The turtles and snakes collected on the trip have been treated by Shannon and Smith (1949); the amphibians, by Reese and Firschein (1950). An itinerary of the trip and list of localities cited are included in the first article. As in the previous reports, specimens cited are deposited in the University of Illinois Museum of Natural History. The 24 species and subspecies taken include a new subspecies of Holbrookia propinqua, one state record (Ameiva undulata amphigramma from Puebla), three northern range extensions, and a number of forms of special interest for other reasons. Among these are the first specimens of Cnemidophorus deppii oligoporus to appear since the original description of the subspecies. We are indebted to Dr. H. M. Smith for his assistance and advice throughout this study. We are further indebted to Dr. Smith and to Dr. E. H. Taylor for permission to use their manuscript of the forthcoming check-list and key to the reptiles of Mexico. Without the generous support extended to the members of our party by the director of the University of Illinois Museum of Natural History, Dr. D. F. Hoffmeister, the project would never have materialized.