156 



BULLETIN 114, UNITED STATES NATIONAL MUSEUM. 



The black rings tend to extend their width dorsally at the expense 

 of the red, and to become narrowed on the sides. They may com- 

 pletely obliterate the red toward the end of the tail, but on the body 

 are usually widely separated. 



The head is black, except for the region anterior to the frontal 

 plate, which is much lightened or mottled with dark and light. In 

 some individuals from the interior this condition is restricted to the 

 extreme anterior end. It is in contrast with the black snout with 

 light cross band of polyzona, and the entirely black snout of annulata. 



Fio. 47.— Map showing locality records for Lampropeltis trlangulxjm nelsoni. 



The dental characters, as indicated by the examination of a few 

 specimens, are as follows: maxillary teeth, 12 or 13, subequal, 

 except that the last two are somewhat enlarged; mandibulars, 13 

 to 15, decidedly larger anteriorly, decreasing posteriorly; palatines, 

 10 or 11, subequal; pterygoids, 18 to 22, smaller than palatines and 

 decreasing posteriorly. 



Habitat and Jiahits. — Nothing is recorded on this subject for this 

 form. 



Range. — At present nelsoni is known only from western Mexico, 

 from Acambaro in the state of Guanajuato to southern Sinaloa and 

 south to Colima, including the Tres Marias Islands. Its southern 

 limit may be looked for in Michoacan or Guerrero, where its range 



