Remarks.—Martin (1958) was the first author to point out that S. campi was probably a subspecies of the more southern S. cystignathoides. Various references in the literature might lead one to believe that the two were sympatric over much of northeastern México; this error was created by the use of a single character (condition of the skin of the venter) to characterize the two populations. Specimens from southern Texas have a smooth venter, lack interorbital bars and have, in general, a brown ground color, whereas specimens from central Veracruz have an areolate venter, interorbital light and dark bars and a yellow ground color. In southern Tamaulipas and eastern San Luis Potosí, these characters vary discordantly, thereby strongly suggesting that the two populations intergrade. Both populations agree in other morphological characters; therefore, they are here treated as geographic variants.
Etymology.—Named for the collector of the type specimens, Mr. R. D. Camp of Brownsville, Texas.
Distribution.—Lower Río Grande embayment in Texas to central Nuevo León and Tamaulipas, México. Intergrades are known from southern Tamaulipas and adjacent San Luis Potosí, México (Fig. 5).
Specimens examined.—(113) TEXAS, Cameron Co.: MCZ 10277-85, 10286 (10); Brownsville, AMNH 3215, 3218-20, 3221 (3), 5376, 62117, FMNH 105336, KU 8135-39, MCZ 3738-42, 3743 (10), TCWC 5908, 7139, TNHC 92-94, 20909, UMMZ 51760, 54031 (5), USNM 52290 (holotype); 22 mi. SE Brownsville, TNMC 14223; 8 mi. SW Brownsville, UMMZ 101127 (3); Harlingen, AMNH 62118, UMMZ 105200-205, 105206 (5), 105207 (4). Hidalgo Co.: Bentsen-Río Grande State Park, UMMZ 114378; 6 mi. S McAllen, TNHC 7136-39; Santa Ana Refuge, TCWC 13495-96; Weslaco, TCWC 17658-60.
MEXICO, Nuevo León: Salto Cola de Caballo, AMNH 57953-54, FMNH 30644-45, 37169-70; Monterrey, UIMNH 13324; 40 km. SE Monterrey, UIMNH 3686. Tamaulipas: 80 km. Matamoros, FMNH 27150 (13).
Fig. 4: Syrrhophus cystignathoides campi (left, TCWC 13490) and S. c. cystignathoides (right, KU 105500). Dorsal views ×2, sides of heads ×3.
Intergrades [S. c. cystignathoides × S. c. campi (88)] MÉXICO, San Luis Potosí: 5 km. E Ciudad del Maiz, UMMZ 106435; 16 km. W Naranjo, FMNH 104584; Salto de Agua, 34 km. WSW Antigua Morelos, TCWC 6980. Tamaulipas: 5 km. W Acuña, 1060 m., UMMZ 101172, 101173 (16), 101174-76, 101177 (6); 14.5 km. NNW Chamal, 430 m., UMMZ 111337 (2); 20 km. NNW Chamal, 700 m., UMMZ 111338 (11); 8 km. N Gómez Farías, 450 m., UMMZ 101165; 8 km. NE Gómez Farías, Pano Ayuctle, UMMZ 102264, 102924 (6); 8 km. NW Gómez Farías, 1060 m., LSUMZ 11084, UMMZ 101199, 102928 (5), 102929-32, 110124 (3); Río Guayala, near Magiscatzin, MCZ 24138-42, 85071-81, UMMZ 88242 (2); Magiscatzin, TCWC 6981; Las Yucas, north of Aldama, MCZ 29665-68; 16 km. NE Zamorina, UMMZ 101124.