_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 Analysis of Characters Characters showing inter-specific and intra-specific variation and that have a wide range of variation were analyzed statistically, when possible, in order to determine extent of variation. One character (see table 3) was analyzed for sexual dimorphism, and for it the coefficient of difference is also given. The statistical terms and formulae have been adopted from Mayr, Linsley and Usinger (1953). Dorsal head shields varied individually and were of no taxonomic importance. Osteological and hemipeneal characters did not show enough variation to be considered here. Scutellation