REVISION OF THE KING SNAKES. 

 Scale formulae of polyzona. 



145 



Locality. 



21-23-21-19 



21-19 



21-19-17 



r.n'l 



19-21-19-17 



19-17 



Male. 



Female. 



Male. Female. 



Male. 



Female. 



Male. 



Female. 



Vera Cruz 



6 

 3 



7 



1 





10 



4 

 1 





Guatemala and Chiapas . . . 

 Yucatan 



1 2 











1 

 1 



i 



1 





Hondiuras and Nicaragua . . . 





2 



2 







Costa Rica 













1 



1 





Total 











9 10 



3 



4 



10 



6 



2 













The table of scale formulae proves nothing, but points of interest 

 indicated by it are (1) that the two higher formulae are evenly 

 divided between the sexes, and, of the individuals having the two 

 lower formulae, the majority are males; (2) that the great majority 

 of the individuals from Nicaragua to southern Mexico have the higher 

 formulae; (3) that the lower formulae are much commoner at the 

 extremities of the range; that is, Yucatan, Costa Rica, and Vera 

 Cruz. Boulenger records (1894, 204) the highest number of scale 

 rows, 25, from Tabasco, and the lowest number, 19, from Costa Rica. 

 His two specimens from Guerrero with 21 rows are in keeping with 

 the suspected approach to nelsonl here. 



We may safely say then that in the structural characteristics, 

 ventral plates, and dorsal scale rows, polyzona shows a]:)proach to 

 micropholis in the southern portion of its range and to nelsoni on the 

 west coast of Mexico. Discussion of other structural characters can 

 not be profitably undertaken here because the specimens at hand are 

 too few to prove anything by figures. It can onl}'' be remarked that 

 there appears to be nothing to refute the testimony of the ventrals 

 and scale rows. 



The striking characters of the pattern of polyzona are (1) the black 

 head with white crossband on the snout; (2) the black tips on the 

 yellow and the red scales; (3) the narrow yellow annuli not widening 

 on the sides. 



The white snout band may be V-shaped, pointing backward, and 

 divided on the middle line, represented only by a few dots in the 

 loreal region, of irregular outline, or prominent, well defined, and con- 

 tinuous across the snout. It appears to be most often poorly devel- 

 oped in Vera Cruz; in two from Yucatan it is absent; from Chiapas 

 to Nicaragua it is usually weU developed; two specimens from Costa 

 Rica show it broad and transverse. This seems to be a change in the 

 extreme south toward micropholis, and in the north appears like a 

 primitive or an extreme condition, certainly not a typical one. 



