130 BULLETIN 61, UNITED STATES NATIONAL MUSEUM. 



Affinities. — Little reliance can be placed on efforts to determine in 

 more than a general way the affinities of this form, but something 

 can be done in this direction. In the first place, if we can pin our 

 faith to the constancy of the trait, the position of the lateral stripe 

 on the second and third rows at once excludes scalaris from the Radix 

 and Sauritus groups. On the basis of our classification, then, it is 

 to be referred either to the Sirtalis or Elegans groups. The latter 

 has otherwise, so far as we know, no representatives in this region, 

 but the ground for referring it to this group is mostly the negative 

 one that the former group (Sirtalis) covers the same territory as 

 scalaris, which argues against a relationship in this direction. 



If scalaris is a derivative of the Elegans group it is quite important 

 that its relationship with melanogaster (the nearest form, geographic- 

 ally, of the same group) be determined by careful collecting and 

 observation. From the present data the ranges of the two forms 

 seem to overlap in southern Mexico, but the habitats of the two may 

 be quite distinct, a conclusion that is strengthened by the fact that 

 on Mount Orizaba scalaris is found, to some extent at least, at a 

 considerable altitude. On the other hand, it is not impossible, and 

 I rather incline toward the hypothesis, that scalaris is more closely 

 related to elegans than to any other form, and represents an ofi'shoot 

 of the latter which has pushed southward from the range of elegans, 

 in the mountains of eastern Mexico. In defense of this view, it is 

 interesting to note that elegans prefers comparatively high altitudes 

 in the Rocky Mountains. At any rate, it is, as known at present, a 

 well-defined form, which is liable to confusion only with plienax. Its 

 relations to phenax will be discussed in considering the affinities of 



the latter. 



PHENAX. a 



Description. — The status of this form is much the same as that of 

 scalaris. At the present time I know of but two specimens in Ameri- 

 can museums. Cope writes that specimens have been sent to both 

 the Academy of Natural Sciences of Philadelphia and the U. S. 

 National Museum, and records six specimens from the latter institu- 

 tion, but the only ones that I have been able to find in either museum 

 is the type and a small individual, both in the National Museum. 

 The proportions and scutellation of these specimens is given in the 

 following table: 



a Thamnophis phenax (Cope), Proc. Acad. Nat. Sci. Phila., 1868, p. 134. 



