104 BULLETIN 17 5, UNITED STATES NATIONAL MUSEUM 



higher number of supralabials, infralabials, and postoculars in males, 

 sayi disagrees with the tendencies common to affinis, vertebralis, and 

 the three subspecies of catenifer, which in every case are toward a 

 higher number in females than in males. In lineaticollis and deppei, 

 however (as well as can be judged from the limited series of specimens), 

 the postoculars, and supralabials and infralabials are all higher in 

 males than in females, as are the infralabials and postoculars in 

 melanoleucus, and the infralabials in mugitus and lodingi. It must be 

 remembered that in these latter cases the numbers of specimens are 



27 



32 48 



36 



30 



27 



J I < I 



^___— 



0.150 

 0.145 

 0.140 

 0.135 

 0.130 

 0.125 

 0.120 

 0.115 

 0.110 

 0.105 

 0.100 



Region No. 12 3 4 5 6 



FiouBE 56.— Geographic variation in ratio of tail length to total length in Pituophis saj/i savl. 



so small as possibly to be deceiving, although the same cannot be 

 said of sayi. 



Four specimens (less than 2 percent of the specimens examined) had 

 only two prefrontals instead of four. 



A 2-headed specimen (U.S.N.M. No. 25398) had two well-formed 

 heads, which imite to form one body about 2 inches posterior to the 

 neck. The scale counts of the two heads are different, and the right 

 neck is slightly longer than the left. Thus, the right head has 9 

 supralabials, 11 and 12 infralabials, 2 preoculars, and 3 and 4 postocu- 

 lars, a loreal, no azygos, and the rostral penetrating two-thirds of the 

 distance between the internasals; the left head has 8 supralabials, 11 

 and 10 infralabials, 2 preoculars, and 3 and 4 postoculars, a loreal, an 



