_Distribution._--Southern Rocky Mountain Province; southwestern part of the Colorado Piedmont, and Raton Section of the Great Plains, to the east of the Sangre De Cristo Range (see fig. 1). _Distinctive characters._--Yellowish Red (5YR 5/6.5); size medium (see measurements); posterior tongues of premaxillae short; posterior margins of nasals forming a V (see fig. 6); bullae pointed ventrally; interpterygoid space V-shaped, lacking a median spicule; basioccipital narrow. _Comparisons._--From _T. b. pervagus_, topotypes of _T. b. internatus_ differ as follows: uniformly paler, not so reddish; smaller; skull smaller; posterior tongues of premaxillae shorter; bullae smaller, less inflated, and more pointed ventrally; zygomata less angular. For comparisons with _T. b. cultellus_ and _T. b. rubidus_, see accounts of those subspecies. _Remarks._--The dividing line between _T. b. internatus_ and _T. b. cultellus_ is drawn arbitrarily since only one specimen has been collected between La Veta Pass and the border of New Mexico. When Goldman (1936:115) named _T. b. internatus_ he included specimens from Union and Colfax counties, New Mexico, and specimens from Gardner, Colorado (not Garfield as stated by Kelson, 1951:66). The specimens from New Mexico and a specimen from Fishers Peak, Colorado, were subsequently assigned to _T. b. cultellus_ by Kelson (_loc. cit._). The specimen from Fishers Peak shows some characters that might be interpreted as intermediate between _internatus_ and _cultellus_, but shows also some unique characters that can be understood only by further collecting in the regions north and northeast of the type locality of _T. b. cultellus_. Variation is slight in the large series of topotypes of _T. b. internatus_. Specimens from other localities in the western part of the range differ little from the topotypes. Specimens from one mile west of Coaldale have slightly more inflated bullae that are more flattened ventrally. Specimens from five miles south of Cotopaxi also have the bullae more flattened ventrally. Specimens from localities bordering the plains differ from the topotypes and near topotypes, and in general show greater variation from locality to locality. Specimens from 12 miles north of Cañon City are dark, resembling _T. b. rubidus_, but cranially agree with specimens from near Colorado Springs in being indistinguishable from specimens from Salida. Specimens from St. Charles Mesa and Bear Creek near Walsenburg differ from the topotypes in having wider rostra. The specimens from St. Charles Mesa have more inflated bullae.