It is described from southern Texas and east-central Mexico (holotype d; Mexico, San Luis Potosi, Nacimiento del Rio Coy, 13-V-1989; allotype 9, in copula with holotype; both deposited in UNAM, Mexico). The new sp. is similar to G. externus Hag., but is smaller and paler. Males differ structurally from externus by: cerci less keeled ventrally, branches of epiproct less widespread, and anterior surface of penis hood V-cleft, not U-cleft. Females lack vertex spines, 9 externus have lateral vertex spines.