_Syrrhophus teretistes_ Duellman, 1958:2-3, 10-14, pl. 2, fig. 2 [Holotype.--UMMZ 115451, from 4.8 km. NW Tepic, Nayarit, Mexico, 840 m.; collected on August 12, 1956, by William E. Duellman]. Gorham, 1966:167. _Diagnosis._--Medium-sized frogs, males 19.2-23.2 mm. snout-vent length, single known female 24.8 mm. snout-vent; vocal slits in males; finger tips widely expanded; first finger shorter than second; inner metatarsal tubercle about three times size of outer; skin of dorsum shagreened, that of venter smooth; tympanum partially concealed, its diameter 28.6-43.8 per cent of eye in males; ground color brown vermiculated with dark brown to nearly black; upper arm and thigh banded; interorbital light bar absent. _Remarks._--_S. teretistes_ appears to be most closely related to _S. pallidus_; I consider it to be an upland derivative of _pallidus_. Morphologically, the differences between the two are few, but lacking evidence of genetic exchange they are retained as species. _Etymology._--Greek, in reference to the whistle-like nature of the call. _Distribution._--Moderate elevations (840-1200 meters) in the Sierra Occidental of Nayarit, Sinaloa, and Durango, Mexico (Fig. 20). _Specimens examined._--(13) MEXICO, _Nayarit_: 4.8 km. NW Tepic, 840 m., UMMZ 115451 (holotype). _Sinaloa_: Santa Lucia, 1090 m., KU 75263-72; 1 km. NE Santa Lucia, 1156 m., KU 78257; 2.2 km. NE Santa Lucia, 1156 m., KU 78258. DISCUSSION There are relatively few clear-cut morphological differences among the fourteen species now assigned to _Syrrhophus_. The majority of the species are allopatric and differ primarily in color patterns. Sympatric occurrence serves as an indicator of specific distinctness and is one of the more practical tests of species validity when cross-breeding experiments are not possible. Two cases of sympatric occurrence are known for the species of _Syrrhophus_ in western Mexico: _modestus_ and _nivocolimae_ are sympatric in southern Jalisco and _pipilans nebulosus_ and _rubrimaculatus_ are sympatric in southeastern Chiapas. In eastern Mexico, _longipes_ and _verrucipes_ are sympatric in southern Hidalgo, and _longipes_ is sympatric with _cystignathoides_, _dennisi_, and _guttilatus_ in southern Tamaulipas. _Syrrhophus cystignathoides_ and _leprus_ are apparently sympatric in central Veracruz. Subspecific assignments have been made only when there is evidence of intergradation. The sympatric occurrence of morphologically similar species in this genus has led me to adopt a conservative approach to the degree of difference philosophy. I have therefore recognized all morphologically distinct allopatric populations as species. [Illustration: FIG. 21: Generic distributions of _Syrrhophus_ (stipple) and _Tomodactylus_ (hatching). Black areas are zones of intergeneric sympatry.]