Chapter II: Part 2

_Variation._--Six specimens have 173 to 183 (176.5 +- 4.00) ventrals. Five of these snakes having complete tails have 71 to 89 (80.6 +- 7.15) subcaudals; the number of ventrals plus subcaudals varies from 250 to 263 (257.0). In the six specimens the reduction from 19 to 17 dorsal scales takes place between ventrals 84 and 97 (93.2 +- 4.71). Sexual dimorphism is evident in the number of subcaudals; two females have 71 and 76 (73.5), and three males have 82 to 89 (85.3) subcaudals. The longest specimen (ANSP 22424) is a female from San Jose, Costa Rica, having a body length of 660 mm., a tail length of 168 mm. and a total length of 828 mm.

The dorsal coloration (fig. 1, E) varies from a black ground-color with two or four narrow white stripes to a dark brown ground-color with a series of black stripes and four white stripes. In the black specimens there are no dark stripes. The darkest specimen (NMW 16838:1) has only two white stripes; these more or less continuous stripes are on the ventral third of the 2nd row of scales and occasionally on the dorsalmost part of the first scale-row. The venter is immaculate white except for black on the tips of the ventral scales. The dorsum above the 2nd scale-row is uniform black. There are no white stripes on the head.

The palest specimen (NMW 16838:2) has four dorsal white stripes; the lateral pair of these stripes is on the ventral half of the 2nd and the dorsal third of the 1st scale-rows; the dorsolateral pair is on the dorsal two-thirds of the 6th and the ventral third of the 7th rows of scales. This latter stripe is the posterior continuation of the white stripe on the head, which originates immediately posterior to the rostral scale and passes posteriorly along the canthus rostralis and along the lateral margin of the supraocular scale to the nape. Posterior to the place of scale reduction, the dorsolateral white stripe is displaced ventrally one scale-row. Except for black flecks or spots on the lateral margins of the ventrals, the venter is immaculate white. The dorsum above the lateral white stripes is brown and black; there is a pair of dorsolateral white stripes. The dorsal half of the 2nd, most of the 3rd, 4th and 5th rows of scales are black; the dorsal margin of the 3rd, both margins of the 4th, and the ventral margin of the 5th rows are paler brown. The dorsal two-thirds of the 7th, all but the dorsal most part of the 8th, and the middle two-thirds of the 10th scale-rows are black; the areas between are a medium brown.

Only six specimens are available on which to base a description of the variation in this species. Furthermore, there are no juveniles, notes on the colors of living individuals, or photographs of this species.

_Remarks._--Taylor (1955:563-565) hesitantly referred a specimen (KU 35630) from 32 kilometers north of Barranca, Puntarenas Province, Costa Rica, to _Conophis lineatus nevermanni_. This specimen, a female, has 169 ventrals and ventral scale-reduction taking place opposite the 109th ventral; both of these characters are well out of the range of _C. nevermanni_. Furthermore, the ventral margins of the supralabials are brown, and the pale dorsal stripes are tan and too wide for _C. nevermanni_ (compare figs. 1, C and E). The specimen definitely is _C. lineatus dunni_, and corresponds well with another specimen from Costa Rica (ANSP 12232).

The dark brown or black dorsum with two or four white stripes and the presence of eight supralabials having dark brown dorsal margins, in combination with the characters of the genus, serve to distinguish _Conophis nevermanni_ from other Central American snakes.

_Distribution._--Pacific coastal plain of northwestern Costa Rica and the Meseta Central of central Costa Rica (fig. 4).

_Specimens examined._--Total of six, as follows: COSTA RICA: _Guanacaste_: Bebedero, Rio Tenorio, NMW 16838(5). "_San Jose_," ANSP 22424.

=Conophis pulcher= Cope

_Tomodon lineatus_ (in part), Salvin, Proc. Zool. Soc. London,
28:455, 1860.

_Conophis pulcher_ Cope, Proc. Acad. Nat. Sci. Philadelphia,
20(5):308, 1869; Journ. Acad. Nat. Sci. Philadelphia, ser. 2,
8:137, 1876; Bocourt _in_ Dumeril, Bocourt and Mocquard,
Mission Scientifique au Mexique et dans l'Amerique Centrale,
2:646-648, pl. 38, fig. 6, 1886; Ferrai-Perez, Proc. U. S.
Natl. Mus., p. 196, September 28, 1886; Cope, Bull. U. S.
Natl. Mus., 32:77, 1887; Trans. Amer. Philos. Soc., 18:194,
April 15, 1895; Ann. Rept. U. S. Natl. Mus. for 1898, p. 1095,
1900; Alvarez del Toro, Reptiles de Chiapas, pp. 154-155,
1960.

_Tomodon pulcher_, Bocourt, Journ. de Zool., p. 408, 1876.

_Conophis pulcher_ var. _similis_ Bocourt _in_ Dumeril,
Bocourt and Mocquard, Mission Scientifique au Mexique et dans
l'Amerique Centrale, 2:647-648, pl. 38, fig. 6, 1886
[Type.--Museum National d'Histoire Naturelle, Paris, no. 6090;
type locality.--unknown, restricted to Tonala, Chiapas, by
Smith and Taylor (1950:326)].

_Conophis lineatus_, Guenther, Biologia Centrali-Americana, p.
165, March, 1895; Boulenger, Catalogue of the Snakes in the
British Museum (Natural History), 3:122-123, 1896; Stuart,
Occas. Papers Mus. Zool. Univ. Michigan, 292:5, June 29, 1934;
Slevin, Proc. California Acad. Sci. 4th Ser., 23:409, December
29, 1939.

_Conophis pulcher pulcher_, Smith, Journ. Washington Acad.
Sci., 31:121, March 15, 1941; Proc. U. S. Natl. Mus., 92:395,
November 5, 1942; Stuart, Contr. Lab. Vert. Biol. Univ.
Michigan, 65:19-20 (part), March, 1954; Contr. Lab. Vert.
Biol. Univ. Michigan, 68:63, November, 1954; Cochran, Bull. U.
S. Natl. Mus., 220:167, 1961.

_Conophis pulcher plagosus_ Smith, Journ. Washington Acad.
Sci. 31:121-122, March 15, 1941 (Type.--United States National
Museum, no. 109707; type locality: Tonala, Chiapas); Smith and
Taylor, Univ. Kansas Sci. Bull., 33(pt. 2):326, March 20,
1950; Stuart, Contr. Lab. Vert. Biol. Univ. Michigan,
65:19-20, March, 1954; Cochran, Bull. U. S. Natl. Mus.,
220:167, 1961.

_Conophis pulcher similis_, Smith, Proc. U. S. Natl. Mus.,
92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408,
October 29, 1943; Smith and Taylor, Bull. U. S. Natl. Mus.,
187:43-44, October 5, 1945; Univ. Kansas Sci. Bull., 33(pt.
2):43-44, March 20, 1950; Maldonado-Koerdell, Inst. Mexicanos
Recursos Nat. Renov. pp. 132-133, 1953.

_Types._--Three in the United States National Museum, nos. 6751 (2 specimens) and 6803, obtained by Henery Hague. Type locality: "Peten," or "Verapaz," Guatemala. There is much doubt about localities for many of Hague's specimens collected in the 1860's (Stuart, 1948:10). Since _Conophis pulcher_ is found predominantly in semi-arid environments, the types might have come from the semi-arid Cahabon, Negro, or Salama river basins--all places near the sugar plantation that Hague managed at San Jeronimo, Baja Verapaz. Possibly the types were obtained from as far away as the Motagua Valley or the southeastern highlands of Guatemala, both of which areas Hague is known to have visited.

_Diagnosis._--Paravertebral stripes present at least posteriorly (fig. 1, F); eight or ten stripes at mid-body; lateral dark stripe passing through eye anteriorly and including at least upper one-half of second scale-row from neck region posteriorly to place of scale reduction near mid-body; eight supralabials immaculate or having dark ventral margins.

_Variation._--Twenty-six specimens have 161 to 182 (169.5 +- 5.31) ventrals. Eighteen of these snakes with complete tails have 65 to 79 (70.6 +- 3.93) subcaudals; the number of ventrals plus subcaudals varies from 231 to 251 (239.3). In 26 specimens the reduction from 19 to 17 dorsal scales takes place between ventrals 94 and 119 (104.6 +- 4.90). Sexual dimorphism is evident in the number of subcaudals; eleven females have 65 to 71 (68.2), and seven males have 70 to 79 (74.3) subcaudals. The longest specimen (AMNH 58364) is a female from El Zamarano, Honduras, having a body length of 703 mm., a tail length of 164 mm. and a total length of 867 mm. The smallest juvenile (MCZ 49793) from Tegucigalpa, Honduras, has a body length of 162 mm., a tail length of 46 mm. and a total length of 208 mm.

The dorsal ground-color is pale brown or white; black or dark brown stripes are present dorsally and laterally. Normally ten stripes are present at mid-body; the first pair on the first row of dorsal scales; the second pair on the upper half of 2nd and lower part of 3rd rows; the third pair on 4th row; the fourth pair on 7th and sometimes part of 8th rows; the fifth pair (paravertebral stripes) on the 9th row. Posterior to the place of reduction from 19 to 17 rows by the fusion of the 3rd and 4th rows, the third, fourth and fifth pairs of stripes are displaced downward one row. Sometimes the second and third pairs of stripes are fused resulting in only eight stripes at mid-body. On some specimens the fourth and fifth pairs of stripes are close together, but in none are they fused so as to result in a pattern of six stripes at mid-body.

The paravertebral stripes begin anteriorly on the nape or at any point on the anterior one-third of the body and continue as discrete stripes onto the base of the tail. Anteriorly these stripes are always broken into a series of dashes; posteriorly the stripes are continuous. In specimens in which the paravertebral stripes do not begin on the anterior-most part of the body, there is no paravertebral pigmentation anteriorly.

In addition to the paravertebrals, the other dorsal dark stripes are variable. In some specimens the stripes are present anteriorly and gradually disappear near mid-body (the first dark stripe only on three specimens). In other specimens the stripes are present anteriorly as dashes and become continuous at mid-body; in others the stripes are continuous throughout. Posteriorly continuous stripes are of uniform width; anteriorly sometimes they are wide on the tip of each scale and narrow on the base (fig. 1, F). The variation in continuity and width described above is found in all of the dorsal dark stripes.

The ventrals usually have more or less conspicuous dark spots laterally; in some specimens there are no spots. Except for the dark lateral spots, when present, the ventrals are immaculate white. Usually the dorsal ground-color is a pale tan, especially between the first and second, and the third and fourth dark stripes. The areas between the second and third dark stripes and across the dorsum between the fourth stripes on each side are pale brown. In some specimens the dorsum between the paravertebral stripes is still paler brown.

Never is more than the lower third of the supralabials brown. Many specimens have little brown, and others none. In most of those specimens having brown on the supralabials, the chin and infralabials are dusky tan or gray. There is little or no brown on the supralabials or the chin in the northern part of the range (Chiapas), whereas the greatest amount of brown on the labials and chin is found on some specimens from the southern part of the range (Honduras). Since there is considerable variation in the amount of brown on the chin and labials of specimens from single localities, the slight geographic trend in this character seemingly is not significant.

In juveniles six black or dark brown stripes boldly contrast with a white or pale tan ground-color. At mid-body the first pair of dark stripes is on the 1st scale row; the second pair on the 3rd and 4th rows; the third pair on the 7th, 8th and at least the lower half of the 9th rows (fig. 3, B). Ontogenetic change in coloration consists of the splitting of the second and third pairs of dark stripes in the juvenile. The first stripe does not split. Consequently adults have ten dark stripes.

In life an adult from Tonala, Chiapas, had black stripes. The ground-color below the second stripe, and between the third and fourth dark stripes was tan. The area between the second and third dark stripes was reddish-brown, as was the dorsum between the fourth pair of dark stripes, except that the 10th scale-row was paler.

Three excellent photographs of this species have been published under the name _Conophis lineatus_ (Ditmars, 1931:pls. 26 and 27).

_Remarks._--Smith (1941:121-122) described _C. pulcher plagosus_ from Tonala, Chiapas, and characterized the subspecies by its having "(1) the ventrals completely unspotted; (2) secondary lines on paravertebral rows not continuous posteriorly; (3) all other lines on body also somewhat spotted in appearance; (4) dusky markings on chin and supralabial border very dim (less distinct than in _p. pulcher_ or any member of the _lineatus_ series)." Although all Chiapan specimens lack ventral spots, specimens from Guatemala have no spots, small spots, or large spots. Even in specimens from Tegucigalpa, Honduras, the southernmost limit of the range, the spotting varies from a few inconspicuous spots to many large spots. Paravertebral rows were continuous posteriorly in all specimens examined by me. Likewise, all other stripes were continuous bands of uniform width posteriorly, having appeared anteriorly as rows of spots or dashes. The amount of brown on the chin and labials has been shown previously not to be geographically significant. The absence of characters of adequate significance to separate populations precludes the naming of subspecies in this species.

Mertens (1952a:93, and 1952b:61-62) designated three specimens from El Salvador as _C. pulcher plagosus_. In the latter paper, Mertens, on the basis of a description of a specimen of "_C. lineatus_" from Divisadero, El Salvador, given by Schmidt (1928:200), referred that specimen also to _C. pulcher plagosus_. I have examined this specimen and refer it to _C. lineatus dunni_. Although I have not seen Merten's specimens, on the basis of the excellent descriptions given by Mertens (1952b:61-62), I refer the three Salvadoranean specimens to _C. lineatus dunni_.

The presence of paravertebral stripes in combination with the characteristics of the genus distinguish _Conophis pulcher_ from all other snakes in southern Mexico and Central America. The only sympatric species of this genus, _C. lineatus dunni_, differs in that it lacks paravertebral stripes, although it may have a single vertebral stripe. _Conophis lineatus dunni_ has lateral dark stripes that are present on the 3rd and 4th scale-rows, never on the anterior third of the body as in _C. pulcher_. Even in juveniles the third pair of dark stripes includes the lower part of the 9th scale-row in _C. pulcher_, whereas the dorsal most dark stripe of _C. lineatus dunni_ never includes more than the lower part of the 8th scale-row.

_Distribution._--Pacific coastal region of Chiapas, Mexico, southeastward into Guatemala; southeastern highlands and the dry valley of central and eastern Guatemala; Caribbean lowlands of Honduras southward to the region of Tegucigalpa, Honduras (fig. 4).

_Specimens examined._--Total of 27, as follows: GUATEMALA: _no specific locality_, CNHM 22912, NMW 16830. _Jutiapa_: Hacienda Mongoy, UMMZ 106725. _El Progreso_: El Progreso, CAS 67000; _El Rancho_, UMMZ 106724; _San Antonio_, CAS 66999. "Peten," USNM 6751(2), 6803. _Sacatepequez_: Duenas, BMNH 64.1.26.17, 64.1.26.126-127. _Zacapa_: Pepesca, AMNH 72555-56.

HONDURAS: _no specific locality_, AMNH 58364. _Cortes_: San Pedro Sula, CNHM 5295-96. _Francisco Morazan: El Zamarano_, AMNH 70189; Tegucigalpa, MCZ 49785, 49787-88, 49791, 49793, 49795.

MEXICO: _Chiapas_: _Soconusco_, UIMNH 33646-47; Tonala, USNM 109707.

=Conophis vittatus= Peters

_Tomodon lineatum_ (in part), Dumeril, Bibron and Dumeril,
Erpetologie Generale, 7(pt. 2):936-938, February 25, 1854.

_Conophis vittatus_ Peters, Monatsb. Akad. Wiss. Berlin, pp.
519-520, pl., fig. 3, October, 1860; Cope, Proc. Amer.
Philos. Soc., 11:162, 1870; Bocourt _in_ Dumeril, Bocourt and
Mocquard, Mission Scientifique au Mexique et dans l'Amerique
Centrale, 2:644-646, pl. 38, fig. 7, 1886; Guenther, Biologia
Centrali-Americana, p. 165, March, 1895; Boulenger, Catalogue
of the Snakes in the British Museum (Natural History),
3:123-124, 1896; Cope, Amer. Nat., 30:1024, 1896; Ann. Rept.
U. S. Natl. Mus. for 1898, pp. 1094-1095, 1232, 1900; Gadow,
Proc. Zool. Soc. London, 2:225, 1905; Amaral, Mem. Inst.
Butantan, 4:211, 1929; Gadow, Jorullo, p. 55, 1930; Smith,
Zool. Ser. Field Mus. Nat. Hist., 24:31-32, January 30, 1939;
Taylor and Smith, Univ. Kansas Sci. Bull., 25:252-253, pl. 23,
July 10, 1939; Stuart, Contr. Lab. Vert. Biol. Univ. Michigan,
65:23, March, 1954; Alvarez del Toro, Reptiles de Chiapas, pp.
153-154, 1960.

_Conophis lineatus_ Cope, Proc. Acad. Nat. Sci. Philadelphia,
16(3):167, 1864 [_nec_ Dumeril, Bibron and Dumeril,
Erpetologie Generale, 7(pt. 2):936-938, atlas, pl. 73,
February 25, 1854; specimen from Colima]; Sumichrast, Arch.
Sci. Nat., p. 246, 1873.

_Tomodon vittatus_, Bocourt, Journ. de Zool., p. 407, 1876.

_Conophis sumichrasti sumichrasti_ Cope, Journ. Acad. Nat.
Sci. Philadelphia, ser. 2, 8:137, 1876 (Types.--United
States National Museum, nos. 29123, 30258; type
locality.--Tehuantepec, Mexico); Bull. U. S. Natl. Mus.,
32:77, 1887; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt.
2):334, March 20, 1950; Maldonado-Koerdell, Inst. Mexicanos
Recursos Nat. Renov., p. 124, 1953.

_Conophis sumichrasti viduus_ Cope, Journ. Acad. Nat. Sci.,
Philadelphia, ser. 2, 8:137, 1876 (Type.--United States
National Museum, no. 30259; type locality.--Tehuantepec,
Mexico); Bull. U. S. Natl. Mus., 32:77, 1887; Cochran,
Bull. U. S. Natl. Mus., 220:167, 1961.

_Conophis sumichrasti_, Cope, Proc. Amer. Philos. Soc.,
18:271, August 11, 1879; Sumichrast, Bull. Soc. Zool. France,
p. 182, 1880; Cope, Trans. Amer. Philos. Soc., 18:194, April
15, 1895; Cochran, Bull. U. S. Natl. Mus., 220:167, 1961.

_Tachymenis lineata_ (in part), Garman, Mem. Mus. Comp. Zool.,
8:60-61, July, 1884.

_Conophis vittatus sumichrasti_, Cope, Ann. Rept. U. S. Natl.
Mus. for 1898, p. 1095, 1900.

_Conophis vittatus videns_ Cope, Ann. Rept. U. S. Natl. Mus.,
for 1898, p. 1095, 1900 (apparent _lapus_ for _viduus_).

_Conophis vittatus vittatus_, Cope, Ann. Rept. U. S. Natl.
Mus. for 1898, p. 1095, 1900; Smith, Journ. Washington Acad.
Sci., 31:119-120, March 15, 1941; Proc. U. S. Natl. Mus.,
92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408,
October 29, 1943; Ann. Carnegie Mus., 30:91, November 2, 1944;
Smith and Taylor, Bull. U. S. Natl. Mus., 187:44, October 5,
1945; Smith, Rev. Soc. Mexicanos Hist. Nat., 7:71, December,
1946; Smith and Taylor, Univ. Kansas Sci. Bull., 33(pt.
2):331, March 20, 1950; Davis and Smith, Herpetologica, 8:134,
January 30, 1953; Maldonado-Koerdell, Inst. Mexicanos Recursos
Nat. Renov., p. 130, 1953; Peters, Occas. Papers Mus. Zool.
Univ. Michigan, 554:22, June 23, 1954; Duellman, Occas. Papers
Mus. Zool. Univ. Michigan, 560:15, October 22, 1954; Webb and
Fugler, Herpetologica, 13:35, March 30, 1957; Duellman, Occas.
Papers Mus. Zool. Univ. Michigan, 589:15, March 21, 1958;
Zweifel, Amer. Mus. Novitates, 1949:2, 5, June 17, 1959;
Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 15(1):91-92,
December 20, 1961.

_Conophis vittata_, Gadow, Proc. Zool. Soc. London, 2:196,
1905; Through Southern Mexico, p. 181, 1908.

_Conophis viduus_, Smith, Zool. Ser. Field Mus. Nat. Hist.,
24:31, January 30, 1939; Hartweg and Oliver, Misc. Publ. Mus.
Zool. Univ. Michigan, 47:26-27, July 13, 1940.

_Conophis vittatus viduus_, Smith, Journ. Washington Acad.
Sci., 31:120-121, March 15, 1941; Proc. U. S. Natl. Mus.,
92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:408,
October 29, 1943; Woodbury and Woodbury, Journ. Washington
Acad. Sci., 34(11):370, 1944; Smith and Taylor, Proc. U. S.
Natl. Mus., 187:44, October 5, 1945; Univ. Kansas Sci. Bull.,
33(pt. 2):340, March 20, 1950; Werler and Smith, Texas Journ.
Sci., 4:565, fig. 16, December 30, 1952; Maldonado-Koerdell,
Inst. Mexicanos Recursos Nat. Renov., p. 130, 1953; Davis and
Dixon, Proc. Biol. Soc. Washington, 72:82-83, July 24, 1959.

_Conophis vittatus vittatus_ x _Conophis vittatus viduus_,
Alvarez del Toro and Smith, Herpetologica, 12:13, March 6,
1956.

_Type._--Zoologisches Museum Berlin. Type locality not given, for the specimen was purchased from a dealer in Hamburg. The type locality was first restricted to "Acapulco," Guerrero, by Smith (1941:119), then to Laguna Coyuca, Guerrero, Mexico, by Smith and Taylor (1950:331).

_Diagnosis._--Three or four dorsal dark stripes, each involving two or more adjacent scale-rows; never having brown or black on the 1st scale-row; seven supralabials immaculate white or pale tannish-white.

_Variation._--One hundred seventy-one specimens have 149 to 181 (163.7 +- 6.33) ventrals. One hundred fifty-three of these having complete tails have 55 to 76 (64.8 +- 4.90) subcaudals; the number of ventrals plus subcaudals varies from 214 to 245 (228.5). In 170 specimens the reduction from 19 to 17 dorsal scales takes place between ventrals 84 and 118 (102.3 +- 6.60). Sexual dimorphism is evident in the number of subcaudals; 58 females have 55 to 66 (60.0) and 95 males have 59 to 76 (67.8) subcaudals. The longest specimen (AMNH 68004) is a male from Escurano, Oaxaca, Mexico, having a body length of 668 mm., a tail length of 182 mm. and a total length of 850 mm. A juvenile (CNHM 40435) from Tehuantepec, Oaxaca, Mexico, has a body length of 133 mm., a tail length of 31 mm. and a total length of 164 mm.

Variation in coloration is of such magnitude that it has been used as the basis for recognition of subspecies. Unfortunately, until this time, most specimens reported upon in the literature represented the two extremes of variation. After examining the coloration of 174 specimens with respect to geographic distribution, I conclude that only one highly variable species is represented. Specimens from the northern and western parts of the range (Michoacan, Colima, and Durango) have the color pattern of _C. vittatus_ as described by Peters (1860:518-521); these snakes have four narrow black stripes on a white or pale tan background, and an immaculate white venter. The lateral dark stripe, which on the head passes through the eye, is present on the dorsal half of the 3rd and the ventral half of the 4th scale-rows; the dorsolateral dark stripe, which passes along the middle of the head and splits on the nape, is present on the middle of the 8th scale-row. The other extreme in color pattern consists of three broad stripes; the two dorsolateral stripes are fused. This pattern is prevalent in specimens from the area around Tehuantepec, Oaxaca. The lateral stripes include the dorsal half to two-thirds of the 2nd, all of the 3rd and 4th, and half of the 5th scale-rows; the fused dorsolateral stripes sometimes cover all of the area dorsal to and including the dorsal third of the 7th scale-row.

Snakes from areas between Tehuantepec and the margins of the distribution of this species are variously intermediate between the extremes described above. In some snakes from these areas the lateral stripes are broad and include either the dorsal half of the 2nd scale-row or the ventral half of the 5th scale-row, but not both on the same specimen. Also, the dorsolateral stripes are broad and include most of the 9th and a part of the 10th scale-rows. Many specimens from the area around Tehuantepec, where the three-striped pattern is prevalent, have an intermediate pattern. Some have white on the center of the 10th scale-row or lateral stripes that are not so broad as to include the 3rd and 4th and half of each of the 2nd and 5th scale-rows.

The supralabials are immaculate white or pale tan, except that in some specimens the dorsalmost part of some supralabials are dark brown or black as they are included in the ventral boundary of the dark stripe that passes through the eye. There are no dusky markings on the chin or on any of the ventral scales.

There is no ontogenetic change in color pattern; juveniles have the same coloration as adults from the same geographic area.

Color in life is not greatly different from that of preserved specimens. One specimen (UMMZ 114483) from 10.8 miles south of Oaxaca, had in life black stripes, a pale yellowish tan dorsal ground-color and a pale off-white venter.

An excellent photograph of this species appears in Schmidt and Inger (1957:230) under the name _Conophis lineatus_.

_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, Michoacan, Morelos and Puebla. Specimens that would have to be considered intergrades between the "subspecies" are found in Michoacan, 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 Mexican snakes. The only other snake that occurs in western Mexico 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).

_Specimens examined._--Total of 174, as follows: MEXICO: _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 Ixtapan de la Sal, KU 67648. _Laguna Coyuca_, CNHM 25881, UMMZ 80942. near La Union, AMNH 66337. _Magueyes, Laguna Coyuca_, AMNH 66149. _Playa Encantada_, TCWC 9470. 1 mi. S Tierra Colorada, KU 67649. near _Xaltinanguis, km. 405_, CNHM 104947. _Michoacan_: Coalcoman, UMMZ 104693. _1/2 mi. SE Coalcoman_, UMMZ 104492. _1 mi. N. Coalcoman_, UMMZ 112543. _1 mi. NE Coalcoman_, 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. _Huajintlan, 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 Rio, 6 km. S Tehuantepec_, UIMNH 6144-49, 37117-19, UMMZ 82649-51. _Rincon Bamba_, CNHM 105129-30, UIMNH 17615. _Salazar_, AMNH 66875. _vicinity of Salina Cruz_, UMMZ 82653. _San Geronimo_, 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 Maria (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 Tequisistlan, 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).

The elements are discussed in the following order: nasal region, cranium and associated elements, maxillo-palatal-pterygoid arch, mandible, dentition, and vertebrae.

_Nasal region._--The premaxillary is relatively heavy and has a concavity posteroventrally. The lateral processes slope downward, but remain fairly thick, and do not project far laterally. This shape (fig. 6) tends to strengthen the nasal region; this anterior strengthening may be a reflection of the fossorial habits of these snakes. There are no posterior processes of the premaxillary; thus the line of fusion with the nasals and septo-maxillaries is broad. The nasal plate is more than twice as long as wide. The nasals are relatively flat above, although each curves slightly downward medially and fuses into the medial nasal septum; laterally each nasal is narrower and deflected downward, forming a small dorsal shield over the nasal cavity. The septo-maxillaries are closely associated with the vomers and form the cavity in which the organ of Jacobson is situated. The broad medial part of the septo-maxillary forms the roof and anterior border of the cavity, whereas the anterior part of the vomer contains the main part of the capsule and forms the posterior and most of the lateral borders of the cavity. The vomer has a thin anterior ridge that gradually disappears before it reaches the border of the premaxillary. The vomer is approximately U-shaped, when viewed from below. It has no posterior process and does not articulate with the parasphenoid; there is a sizeable gap between the two bones. The septo-maxillary has a lateral process that terminally is directed slightly anteriorly.

_Cranium and associated elements._--The frontal is almost three times as long as it is wide; it is flat above with an emarginate dorsolateral margin that forms the upper limit of the optic capsule. Ventrally the frontal is concave and forms the median limits of the optic cavity. Farther ventrally the frontal joins with the parasphenoid, which at this place forms the ventral extent of the skull, and together with the basisphenoid forms the ventral part of the posterior three-fourths of the skull. In ventral aspect, the parasphenoid is a long, thin bone, slightly expanded anteriorly. It forms the anterior floor of the optic foramen; whereas the frontal forms the anterior roof of the same opening. The frontal and its septo-maxillary process surround the olfactory fenestra. The prefrontal articulates with the anterolateral process of the frontal. The posterior surface of the prefrontal forms the anterior wall of the orbit of the eye. The articulating surface upon which the median process of the maxillary bone rests is situated ventrally. The anterior dorsal surface of the prefrontal, together with the anterolateral edge of the frontal, extends slightly over the nasal cavity, affording some degree of protection for the contained organs and forming the posterior border of the cavity. A small nasal process also extends anteriorly from the ventrolateral surface of the prefrontal. The orbital-nasalis foramen is located in the anterior surface of the prefrontal. The parietals are fused into one large bone that forms the roof and sides of the middle part of the cranial cavity. From its suture with the frontal, the dorsal surface of the parietal is relatively flat in the area bounded laterally by the parietal crests, which extend posteromedially from the anterolateral corners of the bone and converge medially at a point near its posterior margin. A slight posterior extension of the parietal crests forms the supratemporal crest, which is present on the posterior part of the parietal and on the anterior part of the supraoccipital. The postfrontals are attached to the anterolateral processes of the parietal. Together the anterior surfaces of these two bones form the posterior rim of the orbit of the eye. The postfrontal extends laterally and ventrally and has a terminal extension that projects anterolaterally. In an articulated skull the trans-palatine articulates with the ventrolateral articulating surface of the postfrontal. Anteromedially, the parietal forms the roof and posterior margin of the optic foramen. The basisphenoid, which is fused with the parasphenoid, also forms a small part of the posteroventral margin of the optic foramen. The basisphenoid forms the floor of the middle part of the cranial cavity and the ventromedial down-pouching that contains the pituitary body. Posterolateral to the parietal and dorsal to the posterior part of the basisphenoid is the prootic. Laterally this bone is deeply emarginate; posteriorly it forms a large part of the otic notch, through which the columella passes. The columella is a long, thin bony rod that terminates posteriorly in cartilage. It is the cartilagenous part of the columella that connects with the external sound detecting mechanism. There are several foramina on the lateral surface of the prootic. On the anterolateral surface of the prootic, branches of the trigeminal nerve pass through three foramina whereas the facial nerve passes through the single posterior foramen near the otic notch. The squamosal is attached dorsoventrally to the posterior part of the parietal and to the lateral part of the prootic. At this place of attachment there is on the prootic a relatively heavy crest that forms a rather broad articulating base. The squamosal is long, flat, and curves slightly in a dorsal direction throughout its length; it becomes thinner and narrower posteriorly. The posterior third of the squamosal forms a broad base by means of which the squamosal articulates with the quadrate. The columella and the squamosal extend posteriorly beyond the limits of the braincase. Posteriorly the skull consists of four bones: an unpaired median dorsal supraoccipital, an unpaired median ventral basioccipital and two lateral exoccipitals. The basioccipital does not have noticeable pterygoid processes, but is rather smooth ventrally and only slightly emarginate on its posterolateral margins. Posteriorly, this bone forms the ventral part of the occipital condyle. The rest of the condyle, on each side, is formed by the exoccipitals. The exoccipitals also form part of the base to which the squamosal is attached. The exoccipitals extend around the sides of the foramen magnum and meet dorsally. Each exoccipital also forms the posterior part of the otic notch, which traverses the exoccipital. The exoccipitals bear moderate occipital crests that extend posterolaterally across the supraoccipital as branches from the supratemporal crest. The supraoccipital also has a medial crest that extends a short distance posteriorly from the supratemporal crest onto the exoccipitals at their dorsal line of fusion.

_Maxillo-palatal-pterygoid arch._--In an articulated skull, the anterior edge of the maxillary is immediately posterior to the lateral tip of the premaxillary (fig. 7). The maxillary is curved moderately laterally and is not robust at its tip, but it becomes heavier about one-third of its length posteriorly. A dorsomedian process begins at about one-third of its distance from the anterior end; the prefrontal articulates with this process. The process is broad and almost flat, except that at its medial end, an elongate, rounded knob extends ventrally. The dorsomedian process of the maxillary extends toward, but does not meet, a lateral process from the palatine. The maxillary teeth are set in sockets on the ventral surface of the bone. Just posterior to the level of the last prediastemal tooth is the median trans-palatine process that articulates with the anteromedian part of the trans-palatine. Immediately posterior to this process, the maxillary narrows slightly; then it broadens to form an obliquely oriented knob. The posteroventral surface of the posterior knob of the maxillary bears one or two enlarged maxillary teeth. (These teeth are discussed further in the section on Dentition.) The anterolateral part of the trans-palatine articulates with the dorsal surface of the posterior knob of the maxillary. Toward the middle of its length, the trans-palatine narrows considerably; then it broadens again and articulates with the pterygoid. The palatine is slightly rounded at its anterior end, which extends anteriorly to the posterior margin of the vacuity containing Jacobson's organ. The palatine extends posteriorly to the trans-palatine process of the maxilla, where the palatine articulates with the pterygoid. A posterior pterygoid process from the palatine projects posteromedially from the end of the palatine and overlaps the anterior end of the pterygoid. Just less than one-half the distance from the anterior end of the palatine, there is a lateral process that curves ventrolaterally forming a blunt tip posteriorly. Slightly more posteriorly and on the medial side of the palatine, is a medial sphenoid process, which is thin, rather broad, and curves ventromedially; ultimately it comes to lie near the anterior part of the parasphenoid. The palatine teeth are set in shallow sockets on the ventral edge of the bone. Of the bones of the maxillo-palatal-pterygoid arch, those on the pterygoid extend farthest posteriorly. The pterygoid is broad medially and posteriorly, although pointed at its posterior tip. The trans-palatine articulates in a broad line at about one-third of the distance along the lateral margin of the pterygoid. Immediately posterior to this articulation, there is a median ridge on the pterygoid; lateral to the pterygoid ridge is an abrupt hollow, the pterygoid groove. Posteromedially, this groove becomes gradually more shallow and disappears. The dorsal surface of the pterygoid is rounded anteriorly and somewhat flattened posteriorly, whereas the ventral surface is gently rounded along its length, except that there is a high median crest. The pterygoid teeth are situated in shallow sockets along this crest. The teeth diminish in size posteriorly.

_Mandible._--The dentary (fig. 8) is compressed laterally and rounded below. The teeth, which are longest about one-third of the way from the anterior end of the dentary, are set in sockets on the medial side of the bone. The posterior half of the dentary overlies the fused surangular-prearticular part of the articular. Ventrally, the posterior part of the dentary underlies the splenial, which is set in a median trench within the dentary. Near the common suture of the dentary and the splenial is the large inferior alveolar foramen; completely within the splenial and ventral to the inferior alveolar foramen is the anterior mylohyoid foramen. Posterior to the splenial and also forming a part of the ventral surface of the mandible is the wedge-shaped angular, which lies directly beneath the fused surangular-prearticular. As has been implied, the articular, the surangular, and the prearticular are fused. The prearticular part of this bone forms a part of Meckel's canal. In the surangular part, immediately posterior to the end of the dentary, is the large surangular foramen. Lying in a longitudinal axis along the medial surface of the articular is a high crest, dorsal to which is a deep hollow. The lateral wall of the articular above this hollow is thin and rounded dorsally; the ventral surface is uniformly round and slightly curved dorsally, except that it ends with a short tympanic crest, which projects beyond the articulation with the quadrate. Where the quadrate articulates with the dorsolateral surface of the posterior portion of the squamosal, the former is broad and has a high mid-lateral crest, which extends about one-third of the distance down the quadrate before disappearing. The columellar process (the place of fusion of the columella) is about two-thirds of the way down the medial surface of the quadrate. Ventrally the quadrate has a narrow neck dorsal to its articulation with the articular. The articulation is formed by two lateral flanges of the quadrate that fit over a medial ridge formed by the articular.

Dentition

Teeth on the maxillary and pterygoid decrease in size posteriorly, whereas those of the dentary do likewise except for the first one or two that are usually slightly smaller than those immediately posterior. The palatine teeth are subequal in size. The enlarged, grooved teeth on the maxillary are in shallow sockets on the posteroventral surface of the posterior knob of the maxillary. These teeth point posteriorly. The grooves are deep and are situated anterolaterally. One or two enlarged grooved teeth are present on a given maxillary. There seems to be a correlation between the type of preservation, the age of the snake, and the number of grooved teeth. Old (large) individuals always have only one grooved tooth that is rooted and functional, whereas some of the younger animals have two in place. Usually replacement teeth are present in alcoholic specimens, but these unrooted teeth are lost in the preparation of dried skeletons. Thus, it seems that in _Conophis_ only one pair of grooved teeth is functional at any one time, although usually replacement teeth are present behind and beside the functional one. Some specimens have one tooth in the medial socket on one side and one in the lateral socket on the other. Replacement teeth on the maxillary and dentary are present in the buccal tissue on the medial side of the bones, whereas on the palatines and pterygoids, the replacement teeth are present laterally. Apparently there are no significant differences in dentition among the members of the genus _Conophis_.

Vertebrae

The fiftieth vertebra of _Conophis vittatus_ (UMMZ 82642) can be described as follows: The neural spine is elongate, thin and low; the posterior edge is sharply emarginate, and the anterior edge is only slightly emarginate. The zygosphene is thin dorsoventrally; in a ventral or dorsal view the zygosphene has a slightly concave anterior edge, the flat surface of which is oriented ventrolaterally. The centrum is elongate and triangular from below; it is widest at the paradiapophyses and narrowest at the short condylar neck. The condylus is directed posteriorly. The centrum, when viewed laterally, is slightly concave and has prominent subcentral ridges that extend from the median side of the paradiapophysial articular surfaces posteriorly to the neck of the condylus. The paradiapophysial articular surfaces are well developed and have two facets. The diapophysial surface is larger and more spherical than the parapophysial one. The parapophysial process projects beyond the parapophysial articular surface and is nearly even with the lip of the cotyle, which is slightly oval. The neural arch is slightly depressed; its width is somewhat less than the width of the cotyle. The articular surfaces of the postzygapophyses are oval and are directed posterolaterally. There is a strongly developed concave interzygapophysial ridge. A well-developed accessory spine extends laterally beyond the oval articular facets of the pre-zygapophysis and forms a slightly flattened, blunt spine. Excellent drawings of the middle thoracic vertebra of _Conophis lineatus dunni_ from Honduras were published by Auffenberg (1958:6).

Hemipenes

The hemipenes of _Conophis_ are moderately caliculate, having spines covering the surface from the base to near the apex (fig. 9). These spines are largest near the base and are reduced to small papillate projections near the apex. The apex terminates in a small disc having three to five laminae in _C. vittatus_ and one lamina in _C. lineatus concolor_. The sulcus is bifurcate; the fork is near the base and almost gives the appearance of two sulci on some specimens. Distally the apices are widely separated, and the intervening space gives the hemipenis a slightly bilobed appearance in some species (especially _C. vittatus_) or a deeply bilobed appearance in others (especially _C. lineatus concolor_).

The everted hemipenis reaches posteriorly to the eighth subcaudal scale. The sulcus bifurcates at the third subcaudal scale. The situation is similar _in situ_ (Cope, 1895:pl. 28, fig. 2).

There are no apparent hemipenial differences among the species of the genus _Conophis_. As can be seen in the above description, the hemipenis of _C. vittatus_ is less bilobed and has a more pronounced disc at the apex than the others. The hemipenis of _C. lineatus concolor_ is most bilobed, but has the smallest apical disc. The other species and subspecies vary widely within these extremes.

Food and Feeding

_Conophis_ eats mostly small lizards, especially _Cnemidophorus_. In Mexico _Conophis_ occurs in semi-arid habitat where _Cnemidophorus_ is common. A specimen each of _Conophis vittatus_ and _C. lineatus lineatus_ were obtained while I was collecting _Cnemidophorus_. The only record of _Conophis_ having fed on a warm-blooded vertebrate was obtained in the course of this study, when I recovered from the stomach of a _Conophis lineatus concolor_ (CNHM 36299) from Chichen Itza, Yucatan, a heteromyid rodent (_Heteromys gaumeri_).

Ralph Axtell (personal communication) observed _Conophis_ actively searching for food at dusk. His observations were made near Tehuantepec, Oaxaca, and the snakes were seen to chase lizards of the genus _Cnemidophorus_. Near Alvarado, Veracruz, in the late afternoon, I watched a _Conophis lineatus lineatus_ follow a lizard into a hole.

Mittleman (1944:122) presents the only discussion of the mode of feeding of a captive specimen of _Conophis lineatus_ ssp. When presented with a _Thamnophis_ slightly smaller than itself, the _Conophis_ struck, and within eight minutes immobilized the _Thamnophis_. Within one-half hour the _Thamnophis_ was swallowed. Three days later the _Conophis_ ate another _Thamnophis_, though still distended from its first meal; nine days later it ate a _Storeria_. In the course of several months, the _Conophis_ ate various toads and hylids and two more _Storeria_. Apparently members of the genus _Conophis_ do not constrict their prey, but rely upon a combination of loss of blood and action of the venom to completely immobilize their prey.

Ditmars (1931:pls. 26-27) showed three photographs of "_Conophis lineatus_" (actually _Conophis pulcher_) ingesting another snake, identified by him as a young _Ophis (= Xenodon) colubrinus_.

Effect of Poison

The rear fangs of these snakes are large for the size of the snake. Various collectors have been bitten, and several reports of the effect of the poison have been published. The snakes are aggressive and bite constantly while being handled. A field companion, Dale L. Hoyt, was bitten on the forefinger by a specimen of _C. l. lineatus_ and immediately felt a burning sensation. The finger swelled, much as it would if stung by a wasp, but it returned to normal size in about twenty-four hours. Ditmars (1931:legend pl. 27) reported immediate burning pain and a localized swelling, an inch in diameter and half an inch high, which lasted for several hours. Mertens (1952b:83) reported merely that the hand of the gardener at the Instituto Tropical in San Salvador bled strongly for a full hour. Edward H. Taylor was bitten by a specimen of _Conophis vittatus_ (Taylor and Smith, 1939:252); pain and swelling lasted for some time. Taylor (personal communication) is still troubled by damage incurred by that bite, which apparently resulted in mechanical damage to the second joint of the middle finger, for the joint swells when the finger is used or exercised. William E. Duellman (personal communication) was bitten on the hand in July, 1956. There was immediate pain and localized swelling, both of which disappeared several hours later.

TAXONOMIC RELATIONSHIPS AND EVOLUTION

The genus _Conophis_ is known only from the Recent. Except that _Conophis_ belongs to the subfamily xenodontinae and probably is of New World origin, little is known about the relationships of the genus. Auffenberg (1958) described a new genus and species of fossil colubrid snake from the Miocene of Montana as _Dryinoides oxyrhachis_ and compared it with several recent genera. This specimen, of which there is a relatively complete skull and a series of vertebrae, seems most closely to resemble a specimen of _Conophis lineatus dunni_ (UF 7657) from Honduras, with which it was compared in basic osteology. The two genera could be related, for the progenitors of _Conophis_ possibly inhabited much of North America in the Miocene.

Another possibility is that the main stock of the xenodontines reached South America in earliest Tertiary times, and that the formation of the Panamanian and Colombian seaways that separated South America and Central America from the Late Paleocene to the middle of the Pliocene left the _Conophis_ stock isolated in Middle America where members of the genus dispersed through semi-arid habitats.

Turning our attention now to the species within the genus, instead of the genus as a whole, _Conophis vittatus_ is readily set apart from other members of the genus on the basis of the universal presence of seven supralabials. In basic coloration it also differs, having no stripe on the 1st scale-row, or spots on the venter, and a maximum of four broad stripes on the body. The other species appear to be more closely related; these make up the _C. lineatus_-group. _Conophis nevermanni_ differs so much from the other species that it might be placed in a separate group. Nevertheless, the basic striped pattern, which is masked by the increased melanism of many specimens, indicates that _nevermanni_ is more closely related to the _lineatus_-group than to _vittatus_. The _lineatus_-group, thus, consists of _pulcher_, _nevermanni_ and the three subspecies of _lineatus_. In this group the color pattern is characterized by the high frequency of ventral spotting, darkening of part of the supralabials, dark pigmentation on the 1st scale-row, and more than four dark stripes on the body of adults. _Conophis lineatus concolor_, on which the dark pigmentation on the body apparently is secondarily lost, is an exception.

If differences in color pattern be used as an indication of the relationships between the species and subspecies of the genus _Conophis_, I would consider _C. vittatus_ the most divergent unit. The subspecies of _lineatus_ closely resemble one another and, as a unit, resemble _pulcher_ from which they differ primarily in the position of the dorsalmost stripes. _Conophis nevermanni_ is more divergent than is _pulcher_ from the species _lineatus_, but probably is not so far removed from _lineatus_ as is _vittatus_.

In the light of what has been pointed out immediately above with respect to resemblances of, and differences between, the species, an hypothesis to account for their formation and for their presence in the areas where they are today is the following: Concurrent with climatic fluctuations in the Late Pliocene and Pleistocene, the northernmost population differentiated into the species _vittatus_, and has subsequently spread north and west from the region of Tehuantepec, Mexico. During the same period _nevermanni_ became isolated in northern Costa Rica.

The species _pulcher_ probably differentiated from the remaining _lineatus_ stock during the Early Pleistocene orogenic upheaval in Guatemala. The _pulcher_ stock was isolated on the Pacific Coastal slopes of Guatemala, while _lineatus_ moved through the subhumid corridor of northern Middle America into Mexico and southward toward Costa Rica (Stuart, 1954a). In the Late Pleistocene and Recent, _pulcher_ moved back across the central Guatemalan highlands occupying its present range in northern Middle America. Primarily because of the formation of unsuitable habitat (wet forest) that presently separates the geographic ranges of populations of _lineatus_, this species differentiated into three subspecies.

SUMMARY

The genus _Conophis_ Peters, 1860, contains four species. Three are monotypic and the fourth has three subspecies, making a total of six taxa.

The genus is characterized by maxillary teeth of equal size followed by a diastema and two enlarged grooved fangs. The scales are smooth, in 19 rows at mid-body, and 17 nearer the tail. The anal is divided, apical pits are lacking, the head shields are normal for a colubrid, and the hemipenis is bilobed having many large basal spines.

The six taxa are separated primarily on the basis of color pattern, but characters of scutellation, including numbers of dorsals, ventrals, caudals, and places of reduction of the number of dorsal scale-rows, were analyzed.

Snakes of this genus are distributed throughout semi-arid environments from southern Mexico southward into Costa Rica. They feed upon lizards, primarily of the genus _Cnemidophorus_; in addition they are known to eat small rodents and other snakes.

_Conophis_ is a member of the subfamily Xenodontinae and, as presently understood, has no known living close relatives. A single specimen of _Dryinoides_ from the Miocene of Montana has been compared with this genus. The genus _Conophis_ is thought to have evolved in Middle America. The present distribution and differentiation probably are primarily the result of climatic fluctuations in Middle America, which produced the areas of subhumid environment where _Conophis_ presently lives.

LITERATURE CITED

AUFFENBERG, W.

1958. A new genus of colubrid snake from the Upper Miocene of
North America. Amer. Mus. Novitates, 1874:1-16. February 27.

COPE, E. D.

1861. Contributions to the ophiology of Lower California,
Mexico and Central America. Proc. Acad. Nat. Sci.
Philadelphia, 13:292-306. December 28.

1867. Fifth contribution to the herpetology of tropical
America. Proc. Acad. Nat. Sci. Philadelphia, 18:317-323.
February 20.

1871. Ninth contribution to the herpetology of tropical
America. Proc. Acad. Nat. Sci. Philadelphia, 23(2):200-224.
October 24.

1876. On the batrachia and reptilia of Costa Rica. Journ.
Acad. Nat. Sci. Philadelphia, series 2, 8(4):93-154, 6 pls.

1895. The classification of the ophidia. Trans. Amer. Philos.
Soc., 18:186-219, 33 pls. April 15.

1900. The crocodilians, lizards, and snakes of North America.
Ann. Rept. U. S. Natl. Mus. for 1898, pp. 153-1270, 36 pls.

DITMARS, R. L.

1931. Snakes of the World. New York, The MacMillan Company,
1931. xi + 207 pp., 84 pls.

DOWLING, H. G.

1951. A proposed standard system of counting ventrals in
snakes. British Journ. Herpetology, 1(5):97-99, fig. 1.

DUELLMAN, W. E.

1958. A preliminary analysis of the herpetofauna of Colima,
Mexico. Occas. Papers Mus. Zool. Univ. Michigan, 589:1-22,
March 21.

DUMERIL, A. M. C., BIBRON, G., AND DUMERIL, A. H. A.

1854. Erpetologie generale, ou histoire naturelle des
reptiles. Paris, 7(pt. 2):xii + 785. February 25.
Atlas, 24 pp., 108 pls.

DUMERIL, A. H. A., BOCOURT, M., AND MOCQUARD, F.

1870-1909. Mission Scientifique au Mexique et dans l'Amerique
Centrale ... Etudes sur les Reptiles. Paris, vol. 2:xiv +
1012 pp., 77 pls.

GARMAN, S.