|(.82-.83) |(.51-.58) |(.42-.44) |(.58-.78) ---------------------+-----------+-----------+------------+---------- Thus far, _G. flavomarginatus_ is known only from the three localities represented in the type series and from the indefinite locality, "Bolson de Mapimí", Chihuahua, given by Duges (1888:146-7, and 1896:479). These long-doubted references of Duges to _Gopherus polyphemus_ seem clearly to represent _G. flavomarginatus_, which probably occurs in several or all of the internally drained basins in northeastern Chihuahua, western Coahuila, and northern Durango. This region is within the Basin and Range physiographic province of Fenneman (1931:326-8) and the Mapimí biotic province of Smith (1949:231). Duges (_supra cit._) seems to have used "Bolson de Mapimí" in a restricted sense, as it is shown on some recent maps (Nat. Geog. Soc., Map of Mexico and Central America, 1953) (American Geog. Soc., Culican Map, NG 13, 1935). Other maps show this bolson to include internally drained portions of the Mexican highlands from northeastern Chihuahua to the region near Lerdo and Torreon. Thayer (1916:73) pointed out that the Bolson de Mapimí, in its larger sense, consists of a series of basins separated by mountains of considerable elevation. The range of _G. flavomarginatus_ appears to be limited ultimately by the higher elevations of the Sierra Madre Occidental and the Sierra Madre Oriental to the west and east, respectively, and to the south by the Mexican plateau. The northern limits of the range are less clear; possibly the range extends as far as the portions of the United States adjacent to northeastern Chihuahua, but this is doubtful. The range seems not to overlap that of any other species of _Gopherus_, although the ranges of _G. flavomarginatus_ and _G. berlandieri_ closely approximate each other in central Coahuila. In September, 1958, when I was collecting turtles near Cuatro Cienegas, Coahuila, I took the opportunity to query natives, as well as an American rancher, about the possible occurrence of tortoises in the area. Most persons had seen no tortoises in the area or said they had seen them only rarely. Several older men who had herded goats in the area all their lives said that tortoises (referred to as "Tortuga del Monte") were common on the other side of the Sierra de La Madera and Sierra de La Fragua ranges west of Cuatro Cienegas. These men referred probably to _G. flavomarginatus_. Americanos lies approximately 75 miles west-northwest of Cuatro Cienegas.