The absence of paravertebral stripes, the presence of a lateral dark stripe on the nape involving the 3rd and 4th rows of scales, and the darkly pigmented 1st scale-row, in combination with the characteristics of the genus, distinguish _C. l. dunni_ from all other snakes in México and Central America. The only sympatric species of this genus, _C. pulcher_, differs in that it has paravertebral stripes (though never a vertebral dark stripe). _Conophis pulcher_ has a lateral dark stripe that includes the upper half of the second scale-row on the anterior part of the body; stripes of _C. l. dunni_ never include more than the 3rd and 4th rows. Even as juveniles the paravertebral row is not darkly pigmented in _C. l. dunni_ as it is in _C. pulcher_. _Distribution._--Semi-arid habitats from sea level to elevations of 1000 m. from the Cuilco Valley in western Guatemala, El Peten and British Honduras southeastward to northeastern and southern Honduras, western Nicaragua and northwestern Costa Rica (fig. 2). _Specimens examined._--Total of 41 specimens, as follows: BRITISH HONDURAS: _Cayo District_: Augustine, ERA-WTN BH-300; _Mountain Pine Ridge, 10 mi. E Augustine_, ERA-WTN BH-298. COSTA RICA: _no specific locality_, AMNH 17309. "_Cartago_," BMNH 71.11.22.15. _Puntarenas_: 32 km. N Barranca, KU 35630; Esparta, USNM 37758. "_San José_," ANSP 3480, 12232. EL SALVADOR: _Morazan_: El Divisadero, CNHM 10999. _San Miguel: San Pedro_, MCZ 57061. GUATEMALA: _El Petén_: Sojio (Toocog), AMNH 69969, 69986. _Huehuetenango_: flood plain Río Cuilco, W of Finca Canibal, 18 km. N Tacaná, UMMZ 98283. _Santa Rosa_: Santa Rosa, UMMZ 107339. HONDURAS: _no specific locality_, AMNH 32814, UF 7657. _Cortes: Cofradía_, SU 8422; _Gracias_, CNHM 28560; _Hacienda de Santa Ana, W San Pedro Sula_, CNHM 5297; San Pedro Sula, UMMZ 68695(2); _near San Pedro Sula_, MCZ 27563. _Francisco Morazan: Potrero de Melio, Escuela Agricola Pan-americana_, MCZ 49987; Tegucigalpa, MCZ 49784, 49786, 49789-90, 49792, 49794. MÉXICO: _no specific locality_, BMNH 53.2.4.16. NICARAGUA: _no specific locality_, UMMZ 65633, USNM 25237. _Leon_: El Polvón, MCZ 5645, 5696. _Managua_: Managua, USNM 79963-64; _3 mi. SW Managua_, KU 42315; _8 mi. WNW Managua_, KU 42314; _1 mi. N Sabana Grande_, KU 42311-13. _Matagalpa_: 1.5 mi. N Matagalpa, UMMZ 116537. =Conophis lineatus lineatus= (Duméril, Bibron and Duméril) _Tomodon lineatum_ (in part) Duméril, Bibron and Duméril, Érpétologie Genérale, 7(pt. 2):936-938, atlas, pl. 73, February 25, 1854; Bocourt, Journ. de Zool., 5:406-407, 1876.