Remarks.—I have been unable to find variation of geographic importance in scutellation in this species. A wide range of variation in the characters of scutellation is present in specimens from most localities; it shows no significant clinal or geographic trends. As I have stated previously, in the discussion of variation, coloration has been the feature primarily used by previous workers to distinguish two "subspecies" for this species; C. vittatus vittatus having four black stripes and C. vittatus viduus having three black stripes. Most of the three-striped snakes occur in the vicinity of Tehuantepec, Oaxaca, whereas the four-striped snakes are found near the margins of the range of the species in Durango, Colima, Michoacán, Morelos and Puebla. Specimens that would have to be considered intergrades between the "subspecies" are found in Michoacán, Guerrero, Oaxaca and Chiapas. At the time the subspecies were proposed only specimens from Tehuantepec or from marginal areas were known. Utilizing the large number of specimens of this species presently available, geographic variation is found to be clinal, from those with three stripes from near Tehuantepec, through several intermediate patterns present on specimens from single localities in Guerrero, Oaxaca and Chiapas, to those with four dark stripes in areas farthest removed to the north and west from Tehuantepec. Since only coloration shows geographic variation, and since this variation represents a continuous cline, subspecies cannot be recognized for this species.

The presence and position of the three or four dark stripes on the body and the absence of brown on the 1st scale-row or on the ventral scales, in combination with the generic characters, distinguish Conophis vittatus from all other Méxican snakes. The only other snake that occurs in western México that has been confused with C. vittatus is Coniophanes piceivittus taylori, which has 25, instead of 19, scale-rows.

Distribution.—Semi-arid habitats on Pacific slopes from extreme southern Durango southeastward to Tuxtla Gutierrez, Chiapas, and inland in the eastern Balsas Basin to Morelos and western Puebla ([fig. 5]).

Fig. 5. Selected locality records for Conophis vittatus.

Specimens examined.—Total of 174, as follows: México: no specific locality, AMNH 66150-52, SU 9465. Chiapas: Piedra Parada, USNM 121453. Pizo de Oro, UIMNH 40821. Tuxtla Gutierrez, Parque Madero, UIMNH 37992-93, 38036-37. Colima: no specific locality, MCZ 46860, USNM 31394, 31396-97. 1 mi. SW Colima, AMNH 12783. S of Manzanillo, AMNH 19641. Durango: Hacienda de Gabriel, AMNH 14217. Guerrero: Acahuizotla, TCWC 7419, 9469. 1 mi. W Acahuizotla, TCWC 7418. 3 mi. W Acapulco, AMNH 71626. 6 mi. E Acapulco, TCWC 9476-77. 10 mi. S Acapulco, TCWC 8578. Agua del Obispo, CNHM 104948, TCWC 11586. near Chilpancingo, MVZ 45067, UMMZ 85722-23. 1 mi. SW Colotlipa, TCWC 9471-74. 2 mi. SW Colotlipa, TCWC 9475. 14 mi. S Ixtapán de la Sal, KU 67648. Laguna Coyuca, CNHM 25881, UMMZ 80942. near La Unión, AMNH 66337. Magueyes, Laguna Coyuca, AMNH 66149. Playa Encantada, TCWC 9470. 1 mi. S Tierra Colorada, KU 67649. near Xaltinanguis, km. 405, CNHM 104947. Michoacán: Coalcomán, UMMZ 104693. 1/2 mi. SE Coalcomán, UMMZ 104492. 1 mi. N. Coalcomán, UMMZ 112543. 1 mi. NE Coalcomán, UMMZ 104692. Puerta de la Playa, UMMZ 105155. 12 mi. S Tzitzio (by road), UMMZ 99153. Morelos: 12 km. NW Axochiapan, TCWC 7311, UIMNH 17613, 25924. 7 mi. SE Cuernavaca, MVZ 32258. Huajintlán, km. 133, CNHM 103270. 12 km. S Puente de Ixtla, km. 133, CNHM 104949. Oaxaca: Bisiliana, AMNH 68010. near Caoba, foot of Cerro Arenal, AMNH 68009. Cerro Arenal, AMNH 68000-03. Cerro de Laollaga, UIMNH 36213. Cerro de San Pedro, UIMNH 17616. Cerro Palma de Oro, UIMNH 37116. "C. Madrena, Sto. T. Quieri," UIMNH 46904. near Chivela, MCZ 25021. Cinco Cerros, UIMNH 37114. Dami Liesa, AMNH 66877, UIMNH 6158, 37115. Escuranos, AMNH 66873-74, 68004-06. Finca Santa Teresa, 2 km. NW Tehuantepec, UMMZ 82648. Huilotepec, AMNH 66878, UIMNH 40820. between Huilotepec and Tehuantepec, AMNH 65106, UMMZ 82644-45. Las Tejas, UIMNH 6151-54. Mixtequilla, UIMNH 6157, 36211. between Mixtequilla Mountains and Tehuantepec, UMMZ 82652. between Niltepec and "Carixxal," AMNH 68876. 10.8 mi. SE Oaxaca, UMMZ 114483. Quiengola, UIMNH 17617. between Quiengola Mountains and Tehuantepec, UMMZ 82647. Rancho Poso Río, 6 km. S Tehuantepec, UIMNH 6144-49, 37117-19, UMMZ 82649-51. Rincón Bamba, CNHM 105129-30, UIMNH 17615. Salazar, AMNH 66875. vicinity of Salina Cruz, UMMZ 82653. San Gerónimo, AMNH 4306, CNHM 1457. San Lucas Ixtepec, UIMNH 36206. San Juan Lajarcia, UIMNH 36212. San Mateo del Mar, AMNH 65914. San Pablo, UIMNH 36207. Santa María (Cerro de Liesa), AMNH 68011. Tapanatepec, MCZ 27806-11. Tehuantepec, AMNH 19644, 65107-09, 65907-13 plus 7, 66871-72, 66879, 68007-08, CNHM 40435-36, 105126-28, MCZ 46403, UIMNH 6150, 17614, 17618, 29692, 36208, 37120-21, UMMZ 82642-43, 82646, USNM 109709-14, 1-2 leagues SSE Tehuantepec, UMMZ 82639-41. Tenango, UIMNH 36209-10. between Tlacolulita and Tequisistlán, CNHM 105125. Yerba Santa, UIMNH 6155-56. Puebla: Atencingo, KU 39626.

Skull

In studying the osteology of the genus Conophis, I have examined two complete skeletons (one C. vittatus and one C. lineatus); two additional skulls of C. vittatus and C. lineatus; and 24 sets of dentigerous bones, representing all of the species. Terminology of the skeletal elements is that of Duellman (1958), Parker (1878), Radovanovic (1937) and Szunyoghy (1932). The drawing of the right side of the skull of a specimen of Tomodon lineatus that appears in Jan and Sordelli (1881:liv. 50, pl. 2, fig. 34) is of little value due to its small size and lack of detail.

The skull of Conophis is typical of a relatively unspecialized colubrid snake. Skulls of Conophis lineatus concolor and C. vittatus closely resemble each other. The following description is based primarily on the skull of C. lineatus concolor (UMMZ S-778).