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BULLETIN 17 5, UNITED STATES NATIONAL MUSEUM 



case in jani, to decrease the proportionate tail length from that 

 typical of de-pjiei (fig. 20), to increase the numbers of ventrals and 

 caudals (figs. 21-23), and to develop stripes, all indicate that deppei 

 is the common ancester of these two forms. The derivation of deppei 



E^S s. af finis 



Figure 18.— Distribution of PUuophis deppei deppei, P. d.jani, P. lineaticoUis, P. saj/t tai/i, and P. s. affinis. 



from sayi affinis is suggested by the contiguous ranges of the two 

 forms and by the similarity in pattern. That deppei is derived from 

 affinis, rather than the reverse, seems probable in consideration of 

 the presence in the former of only two prefrontals, and the contact 



