24 



38. Dorsolateral and ventrolateral dark fields uniform in color, dark edging of pale middorsal 



and lateral stripes not evident; middorsal pale stripe confined to middorsal scale row 

 anteriorly, expanding onto adjacent portions of paravertebral rows posteriorly; scales of 



first dorsal scale row unpigmented on anterior half or more of body T. triseriata 



Middorsal and lateral pale stripes dark edged, this edging darker than dorsolateral and 

 ventrolateral dark fields, middorsal pale stripe occupying middorsal scale row and adjacent 

 portions of paravertebral rows the length of body, upper half of first dorsal scale row 

 darkly pigmented the length of body T. taeniata 



39. Postocular single 40 



Postoculars usually 2 - 43 



40. Head and nape white, remainder of dorsum dark olive T. albiceps 



Dorsal coloration not as above - 41 



41. Dorsum and venter black T. nigra 



Dorsal coloration not as above - 42 



42. Dorsum of head only slightly darker than remainder of body T. gracilis 



Dorsum of head distinctly darker than remainder of body — T. atriceps 



43. Dorsum and venter dark brown to black — T. moesta 



Coloration not as above 44 



44. Color of dorsum of head essentially the same as that of dorsum of body 45 



Color of dorsum of head distinctly darker than that of dorsum of body 49 



45. No pale nuchal band present T. petersi 



Pale nuchal band present 46 



46. Ventrals more than 160 (163-164) - T. bairdi 



Ventrals fewer than 155 47 



47. Pale preocular spot absent, pale postocular spot present or not T. schistosa (part) 



Both pale pre- and postocular spots present 48 



48. Well-developed complete pale nuchal band present, beginning on posterior portion of 



parietals T. alticola (part) 



Poorly-developed broadly middorsally-interrupted pale nuchal band present, confined to 

 scales posterior to parietals - T. tayrae (part) 



