Etymology.—Latin, guttula, meaning spotting or flecking, in reference to the color pattern.
Distribution.—Moderate to intermediate elevations (600 to 2000 m.) along the Sierra Madre Oriental from the Big Bend Region of Texas to Guanajuato, México ([Fig. 10]).
Specimens examined.—(32) TEXAS, Brewster Co.: Juniper Canyon, Chisos Mts., FMNH 27361 (holotype of S. gaigeae), 27360, 27362-63, MCZ 15346, 27801, UMMZ 66080, 66082, 66085-91, USNM 76876; Upper Green Gulch, TCWC 15943.
MÉXICO: Coahuila: 8 km. S Saltillo, UIMNH 55518-21. Guanajuato: Guanajuato, USNM 9888 (holotype of Malachulodes guttilatus); 8 km. E Guanajuato, AMNH 73425; Cerro Cubilete, AMNH 73424. Nuevo León: 3 km. S Galeana, JDL 1215 (skeleton), UIMNH 58204; 24 km. SW Galeana. 1575 m., USNM 108594 (holotype of Syrrhophus smithi). San Luis Potosí: 5 km. SW San Luis Potosí, UIMNH 7807 (holotype of S. petrophilus). Tamaulipas: 1.6 km. NW La Joya de Salas, 1530 m., UMMZ 110736 (4).
Syrrhophus marnockii Cope, 1878:253 [Syntypes.—ANSP 10765-68, from "near San Antonio," Bexar Co., Texas; collected by G. W. Marnock].
Syrrhophus marnocki: Yarrow, 1882:24, 193. Milstead, Mecham, and McClintock, 1950:550.
Diagnosis.—Medium-sized frogs, males 18.4-28.9 mm. snout-vent, females 20.4-35.4 mm. snout-vent length; vocal slits in males; digital tips widened ([Fig. 1]); first and second fingers equal; skin of dorsum smooth to weakly pustular, that of venter smooth; snout blunt, rounded; diameter of tympanum 47.2-68.3 per cent that of eye in males, 45.8-73.3 in females; dorsum tan to light brown in preservative with rusty-brown flecks, venter white; ground color green in life; thighs banded; interorbital bar absent.
Remarks.—Specimens from the southern edge of the Edwards Plateau and the eastern edge of the Stockton Plateau have larger flecks on the back that tend to form a vermiculate pattern like that of S. guttilatus. The vermiculation is never well developed (see plate 38 in Conant, 1958). Most of the specimens from the Edwards Plateau have a punctate pattern ([Fig. 9]).
Fossils are known from the Sangamon interglacial deposits in Foard and Knox Counties, Texas (Lynch, 1964; Tihen, 1960).