132 BULLETIN 61, UNITED STATES NATIONAL MUSEUM. 



Variation. — If the specimens listed in the table are typical of this 

 form, it is interesting to note that the scutellation is somewhat 

 reduced, as shown by the dorsal scale formula of 19-17 and the ten- 

 dency toward the labial formula 7/9. The other scale formulas can 

 not of course be determined on the basis of two specimens, but it is 

 evident that the tail is not long, as in the Sauritus group. 



AJJinities. — As illustrated by the described specimens, the colora- 

 tion of phenax is strikingly characteristic, so that a much larger series 

 of specimens must be examined before a serious attempt can be made 

 to discover its affinities. Unfortunately we do not have the lateral 

 stripe to aid us, as this is obsolete in the specimens examined, so that 

 we must depend on the other characters. That it is not to be referred 

 to the Radix or Sauritus groups seems to be sufficiently indicated 

 by the fact that the forms of these groups, which occur in Mexico, 

 show no tendency to acquire the jilienax tj\)& of coloration, although 

 two forms of these groups (proximus and inegalo'ps) come very close 

 to or possibly overlap the range of phenax. Furthermore, on the same 

 grounds we believe it to be very improbable that the form in question 

 is to be referred to the Sirtalis group." 



The most probable near relative of plienax is, in my estimation, 

 scalaris. Thus, as far as is revealed by the material examined, the 

 scutellation and tail length is exactly similar to that of some speci- 

 mens of scalaris, wliile the coloration of the former resembles that of 

 the latter, as it does no other in the genus. Thus, in scalaris, as 

 already pointed out, the large transverse blotches encroach upon the 

 stripes which are narrow, and it only requires that these blotches 

 of the opposite sides be continued across the back and the stripes 

 entirely obliterated to produce a type exactly like phenax. It is 

 interesting to note that in one specimen of phenax examined the 

 crossbars are interrupted to some extent along the median dorsal line, 

 producing two series of lateral blotches, as in scalaris, and that the 

 general type of coloration exhibited by these two forms occurs 

 nowhere else in the genus. I believe, therefore, that the two 

 are very closely related, and since they are apparently found in the 

 same localities it is most probable that the so-called phenax speci- 

 mens simply represent individuals in which the process leading to 

 the tyi^e of coloration exhibited by scalaris has been continued far- 

 ther to the total obliteration of the stripes and the fusion of the 

 lateral .crossbars across the median region of the back. The dis- 

 tinctness of the form should be adhered to, however, until settled by 

 more extensive investigation. 



«Bocourt (Miss. Sci. Mex., Rept., 1893, p. 778) makes phenax a subspecies of cyrtopsis 

 (eques), thus linking it with the Sirtalis group. I can find no justification for this 

 except the similarity in scutellation, an unreliable factor upon which to base such 

 conclusions, unless it be controlled by others. It will be showni later that eques is 

 represented in this region by one dwarfed form, and that the latter is quite distinct, 

 from phenax. 



