Tachymenis (in part), Garman, Bull. Essex Inst., 16:33, January 9, 1884 (vittatus and lineatus).
Erythrolamprus (in part), Ditmars, Bull. Antivenin Inst. Amer., 2(2):27-29, June.
Coniophanes (in part), Wettstein, Sitz. Akad. Wiss. Wien, mathem-naturw. kl. 143:37-38, 1934 (nevermanni).
Historical summary.—In 1854 Duméril, Bibron and Duméril described and figured Tomodon lineatum from America. In 1860 Peters described and figured as a new genus and species, Conophis vittatus, based on a specimen that he had obtained from a dealer in Hamburg. The provenance of this specimen is not known, for it was discovered aboard a ship near the mouth of the Mississippi River. It was not until 1871 that Cope included lineatus in the genus Conophis. Cope (1861) proposed the name Conophis vittatus (nec Peters, 1860). Later (1900) he changed its name to Conophis lineaticeps. Early uncertainty of the relationships of the species lineatus caused Günther (1858) to place it in the genus Psammophis. With the exception of Garman (1884a and 1884b) who placed lineatus in the genus Tachymenis, and Wettstein (1934) who reported five specimens of Conophis nevermanni as Coniophanes i. imperialis, all specimens reported after 1876 were placed in the genus Conophis.
The only previous attempt to review the systematics of this genus was made by Smith (1941) who based his study primarily on specimens in the United States National Museum. He examined only 28 specimens, including none of one species (nevermanni).
Description.—Hemipenis slightly bifurcate having forked sulcus spermaticus, large spines near base, and smaller spines or papillae on flounces nearer apices; prediastemal maxillary teeth 8-12, subequal in length, and followed by short diastema and one enlarged fang or two; fangs grooved, only one functional at any one time, unless snake is in process of shedding teeth; teeth 6-10 on palatine, 15 to 19 on pterygoid, 15 to 21 on dentary; teeth on dentary decreasing in size posteriorly; large parotid (venom) gland on either side of head in temporal region; head shields of basically unmodified colubrid type excepting decurved rostral; rostral concave below and therein modified for burrowing; internasals and prefrontals paired; nasals divided; loreal single; preocular one, rarely two; postoculars, two; supralabials, 7-8, 3rd and 4th or 4th and 5th under eye; infralabials, 8-11, usually 9 or 10; temporals, normally 1 plus 2 plus 3; chin-shields subequal in length; ventrals, 149-183, rounded and overlapping; caudals, 55-89, paired and imbricate; anal divided; dorsal scales smooth and in 19 rows at mid-body with no apical pits or keels; scale reduction normally involving fusion of 3rd and 4th rows, resulting in 17 scale-rows near tail; tail length more than 20 per cent of body length; maximum total length exceeding 1.1 meters; dorsal color pattern consisting of dark stripes, or no darkening, on paler ground-color; ventral surfaces immaculate pale yellowish or white, except on specimens having single lateral dark spots on some or all ventrals; pupil round; diurnal or crepuscular; feeding primarily on small lizards, sometimes on small mammals or other snakes.
Distribution.—Semi-arid regions of southern México and Central America as far south as Costa Rica.
Key to the Species and Subspecies
Although many juveniles differ greatly in general coloration from the adults, both the juveniles and the adults of any species or subspecies can be identified from the following key; juveniles differ from adults in extent and intensity of dark pigmentation but not in rows of scales involved.
| 1. | Seven supralabials (3rd and 4th below orbit); 3 to 8 dark stripes along body |
| 2 | |
| Eight supralabials (4th and 5th below orbit); unstriped or with more than 4 dark stripes along body, or dark with 2 or 4 pale stripes | |
| 3 | |
| 2. | Dark stripes involving no more than one longitudinal scale-row |
| [C. lineatus lineatus (part), p. 267] | |
| Dark stripes involving at least two adjacent scale-rows | |
| [C. vittatus, p. 277] | |
| 3. | Supralabials having black borders above; head and body generally black with 2 or 4 white lines running length of body |
| [C. nevermanni, p. 272] | |
| Supralabials immaculate or having dark borders below; head and body usually pale with dark stripes, or without stripes | |
| 4 | |
| 4. | Lateral dark stripe through eye involving upper half of second scale-row; dark stripe on paravertebral row, at least posteriorly |
| [C. pulcher, p. 274] | |
| Lateral dark stripe becoming indistinct on body, or restricted to 4th or 3rd and 4th rows anteriorly, not involving 2nd scale-row on anterior 1/3 of body (an auxiliary lateral stripe sometimes present involving 2nd row); no paravertebral stripes | |
| 5 | |
| 5. | Stripes disappearing posteriorly (except for small spots of pigment on scale-row 4 or 7); 1st scale-row unpigmented |
| [C. lineatus concolor, p. 270] | |
| Stripes present posteriorly; 1st scale-row pigmented | |
| 6 | |
| 6. | Lateral stripes narrow on nape, restricted to 4th scale-row on body |
| [C. lineatus lineatus (part), p. 267] | |
| Lateral stripes involving 3rd and 4th rows, at least on nape | |
| [C. lineatus dunni, p. 262] | |