152 BULLETIN 114, UNITED STATES NATIONAL MUSEUM. 



in width; (6) the black tips on most of the yellow scales of polyzona 

 have here become much accentuated; (7) the black tips on the red 

 scales have become reduced in area or have disappeared entirely; 

 (8) the black of the head has receded, leaving a black spot on the 

 upper labials below the eye, and leaving the snout and temples free 

 from black except for a spot on the posterior portion of each scute, 

 and occasional minute mottlings; (9) the number of dorsal scale 

 rows averages decidedly lower. 



The pattern changes represent only a further development of the 

 pattern of polyzona. The structural changes represent normal varia- 

 tion in polyzona and all other forms of the genus, but they are changes 

 that in other forms, notably elapsoides, are associated with speciali- 

 zation. In fact, in every way micropholis gives the impression that 

 it is an end form — quite beyond consideration as an ancestral type. 

 It must then be looked upon as derived from polyzona and not as 

 ancestral to it. 



