_Salvadora mexicana_ inhabits only the arid scrub forest at elevations from sea level to about 1000 meters.

~Sibon nebulatus~ (Linnaeus)

_Coluber nebulatus_ Linnaeus, Systema naturae, ed. 10, 1, p.

222, 1758.--Africa (in error). Type locality restricted to Jicaltepec, Veracruz, Mexico, by Smith and Taylor (1950a:349).

_Sibon nebulatus_, Taylor, Univ. Kansas Sci. Bull., 26:473, November 27, 1940.

Aquila.

The one specimen from Michoacan was collected by Peters (1954:30) in tropical semi-deciduous forest on the coastal foothills of the Sierra de Coalcoman. As presently known, the range of this species in western Mexico extends from Chiapas to Nayarit. Throughout this region the species avoids scrub forest; this may explain its absence in the Balsas-Tepalcatepec Valley.

~Sonora michoacanensis michoacanensis~ (Duges)

_Contia michoacanensis_ Duges, _in_ Cope, Proc. Amer.

Philos. Soc., 22:178, 1885.--Michoacan. Type locality restricted to Apatzingan, Michoacan, Mexico, by Smith and Taylor (1950a:335).

_Sonora michoacanensis michoacanensis_, Stickel, Proc. Biol.

Soc. Washington, 56:116, October 19, 1943.

Apatzingan (3); Coalcoman (3); 12 km. S of Tzitzio.

These specimens, together with all known specimens from the Sierra del Sur in Guerrero (KU 23790-1, MVZ 45123) and the upper Balsas Basin in Puebla (UIMNH 41688), are referable to _S. m. michoacanensis_. The dorsal pattern consists of a highly variable number of cross-bands of red, white, and black. In the specimens from Michoacan there are as many as 17 red cross-bands on the body. One specimen from Apatzingan (CNHM 37141) has just behind the head a white band, bordered on either side by a narrow black band; posteriorly the body is uniform red. Two specimens from Coalcoman (UMMZ 109905-6) have respectively 11 and 13 red cross-bands and 20 and 17 white cross-bands, and the posterior part of the body is devoid of red color. Other specimens from these localities have red, black, and white cross-bands throughout the length of the body.

_Sonora michoacanensis michoacanensis_ is distinguished from _S.

michoacanensis mutabilis_ by the presence of cross-bands on the tail in the latter (Stickel, 1943:116). One specimen from Coalcoman (UMMZ 109904) has one narrow band on the tail; all others from Michoacan have uniformly red tails.

Apparently _Sonora michoacanensis michoacanensis_ ranges in semi-arid and arid habitats from the upper Balsas Basin in Puebla westward to the lower slopes of the Sierra de Coalcoman, whereas _S. m. mutabilis_ lives in foothills of the Sierra Madre Occidental from southern Jalisco to Nayarit. Zweifel (1959b:6) presented evidence to show that specimens of _S. m. mutabilis_ supposedly from "Distrito Federal" probably bear erroneous locality data.

~Tantilla bocourti~ (Gunther)

_Homalocranium bocourti_ Gunther, Biologia Centrali-Americana, Reptilia, p. 149, 1895.--Guanajuato, Guanajuato, Mexico.

_Tantilla bocourti_, Cope, Amer. Nat., 30:1021, December, 1896.

Carapan; Patzcuaro (2); between Zitacuaro and Rio Tuxpan (11).

This small snake is an inhabitant of the coniferous forests and the pine-oak forests on the Cordillera Volcanica. Data on the series from between Zitacuaro and the Rio Tuxpan were given by Taylor (1940c:481).

~Tantilla calamarina~ Cope

_Tantilla calamarina_ Cope, Proc. Acad. Nat. Sci.

Philadelphia, 18:320, February 13, 1867.--Guadalajara, Jalisco, Mexico.

Apatzingan; La Placita.

Although this snake has been collected at high elevations along the rim of the Mexican Plateau in Nayarit, Jalisco, Mexico, and Puebla, the specimens from Michoacan are from arid scrub forest at elevations of less than 400 meters. The species has been found in similar habitats in Colima (Oliver, 1937:24) and in Sinaloa and the Tres Marias Islands (Zweifel, 1960:110).

~Toluca lineata lineata~ Kennicott

_Toluca lineata_ Kennicott, _in_ Baird, Report on the United States and Mexican boundary survey, 2, Reptiles, p. 23, 1859.--Valley of Mexico.

_Toluca lineata lineata_, Taylor and Smith, Univ. Kansas Sci. Bull., 28:343, May 15, 1942.

Capacuaro; Carapan (12); Cheran (23); Cojumatlan; Los Reyes; Morelia (2); Nahuatzen; Paracho (10); Patzcuaro (17); Uruapan (2).

This small snake is an inhabitant of the coniferous forests between elevations of about 1550 and 2800 meters. Not infrequently, individuals have been found in pine-oak forest within these elevations.

The generic status of _Toluca_ is unsettled. Taylor and Smith (1942b) separated _Toluca_ from _Conopsis_ by the presence of enlarged and grooved posterior maxillary teeth in _Toluca_ and their absence in _Conopsis_. Bogert and Oliver (1945:378) suggested synonymizing _Toluca_ with _Conopsis_. Smith and Laufe (1945:12) defined the generic position of _Toluca_. Actually, in deciding the generic position of these snakes, five genera (_Ficimia_, _Gyalopion_, _Pseudoficimia_, _Conopsis_, and _Toluca_) must be considered. Of these _Ficimia_ and _Gyalopion_ are closely related; they have been placed in one genus by some workers.

_Pseudoficimia_ is intermediate between _Ficimia-Gyalopion_ and _Toluca-Conopsis_. A workable definition of the supraspecific cla.s.sification of these snakes must await a thorough review of the species.

~Trimorphodon biscutatus biscutatus~ (Dumeril, Bibron, and Dumeril)

_Dipsas biscutata_ Dumeril, Bibron, and Dumeril, Erpetologie generale, 7 (pt. 2):1153, 1854.--Mexico. Type locality restricted to Tehuantepec, Oaxaca, Mexico, by Smith and Taylor (1950a:340).

_Trimorphodon biscutatus biscutatus_, Smith, Proc. U. S.

Natl. Mus., 91:159, November 10, 1941.

Apatzingan (11); Cofradia; Cuatro Caminos; El Sabino (2); La Placita; La Playa (2); Lombardia (2); Nueva Italia (2); Rio Tepalcatepec, 27 km. S of Apatzingan; Tafetan.

In the arid lowlands of the Tepalcatepec Valley and presumably also in the scrub forest of the coastal lowlands, this is an abundant snake, which is active only at night. Usually snakes of this species are found on the ground, but one large individual was observed at night in a low tree. That individual defied capture by widely opening its mouth and striking repeatedly at the collector. The excreta of one specimen contained feathers of an unidentified species of bird.

~Trimorphodon latifascia~ Peters

_Trimorphodon biscutata latifascia_ Peters, Monats. Akad.

Wiss. Berlin, p. 877, 1869.--Puebla, Mexico. Type locality restricted to Izucar de Matamoros, Puebla, Mexico, by Smith and Taylor (1950a:341).

_Trimorphodon latifascia_. Taylor, Univ. Kansas Sci. Bull., 25:364, July 10, 1939.

Apatzingan (5); Casada Tzararacua; Coalcoman (2); Lombardia; 14 km. S of Lombardia; Nueva Italia; San Salvador.

In Michoacan this species has been collected in semi-arid habitats at elevations from 300 to 1430 meters in the Tepalcatepec Valley and lower slopes of the Cordillera Volcanica. In this area it occurs sympatrically with _Trimorphodon biscutatus biscutatus_.

In life, adults have a pale tan dorsal ground color and rich chocolate brown cross-bands; the eye is pale grayish tan. A juvenile from Coalcoman has black cross-bands on a pale grayish tan ground color. As stated by Schmidt and Shannon (1947:83) and Peters (1954:32), the type specimen of _Trimorphodon fasciolata_ Smith from Cascada Tzararacua is indistinguishable from specimens of _Trimorphodon latifascia_.

Seven males have 209 to 223 (216.5) ventrals; one female has 227 ventrals. The number of dark cross-bands on the body varies from 12 to 16 (13.5). The relationships of this species are with _Trimorphodon tau_ on the Mexican Plateau. In fact, additional specimens from the headwaters of the Tepalcatepec Valley and the lower slopes of the Mexican Plateau in eastern Michoacan and adjacent Jalisco may show that the two are conspecific. _Trimorphodon latifascia_ differs from _tau_ in having fewer dark cross-bands on the body and in lacking an interocular bar.

~Trimorphodon tau~ Cope

_Trimorphodon tau_ Cope, Proc. Amer. Philos. Soc., 11:151, 1869.--Quiotepec, Oaxaca, Mexico.