23 



27. Barely to well-discernible dark nape band present, grading into ground color of dorsum; 



most of intemasals and prefrontals cream colored; well-developed pre- and postocular 



pale spots present T. alticola (part) 



No dark nape band present; intemasals and prefrontals same color as rest of head or 

 only slightly paler; preocular pale spot absent; postocular pale spot usually poorly 

 developed to absent T. schistosa (part) 



28. Subcaudals fewer than 30 (21-26) T. brevicauda 



Subcaudals more than 30 29 



29. Pale lateral stripe occupying row 4 and adjacent halves of rows 3 and 5 30 



Pale lateral stripe occupying adjacent halves of rows 3 and 4 32 



30. Pale nuchal collar not crossing ultimate supralabial T. oaxacae 



Pale nuchal collar crossing ultimate supralabial 3 1 



31. Pale nuchal collar complete; venter essentially immaculate; subcaudals 55 or fewer 



T. flavilineata 



Pale nuchal collar divided medially; well-defined dark stripe present on lateral edges of 

 ventrals; subcaudals 58 or more T. reticulata 



32. Pale nuchal band reduced to two nuchal spots: subcaudals 42 or fewer (31-42) 



T. striata 



Pale nuchal band complete, divided medially, or both medially and laterally 33 



33. Pale middorsal stripe confined to middorsal row 34 



Pale middorsal stripe present on middorsal scale row and adjacent portions of 

 paravertebral rows 3 8 



34. Ventrals fewer than 150 35 



Ventrals 155 or more 36 



35. Pale lateral stripe continues onto distal portion of tail T. tecta 



Pale lateral stripe does not continue onto tail T. trilineata 



36. Ventrals 163 or more (163-172); subcaudals 68 or more (68-72) T. impensa 



Ventrals 161 or fewer; subcaudals 65 or fewer 37 



37. Pale middorsal stripe becoming gradually obscured and fragmented posteriorly; 



subcaudals 56 or fewer (52-56) T. slavensi 



Pale middorsal stripe well developed the length of body; subcaudals 59 or 



more (59-65) T. tritaeniata 



