VARIATIONS OF GAETER-SNAKES. 37 



with the reduction in the number of scale rows. Thus, where the 

 fourth row is dropped posteriori}^ to k^ave 17 the lateral stripe in one 

 form {radix) is left upon the third row only, in two forms (fmtleri and 

 megalops) it descends below the third to include the secon<l, while in 

 three forms {proxinius, sauritus, and sacJceni) it ascends one row after 

 the loss of the fourth, so as to remain posteriorly also upon the third 

 and fourth. In but two forms is the position of the stripes modified 

 anteriorly, and in one of these (marcianus) it is apparently due to 

 the general pallidness of the ground color which partially obscures it; 

 in tlie other {hutleri) we have the only decidedly dwarfetl representa- 

 tive of the forms which have the stripe upon the third and fourth rows. 

 When the scale formula in hutleri is 10-17, the lateral stripe is ante- 

 riorly upon the third and the margins of the second and fourth rows, 

 posteriori}^ upon the second and third. When the scale formula is 

 decreased to 17-19-17, the lateral bands are anteriorly and posteriorly 

 upon the second and third rows, on the midtlle of the body being still 

 upon the second, third, and fourth. In the forms that have the lat- 

 eral stripes upon the thirtl and fourth rows there is thus apparently 

 exhibited a tendency toward producing a form with the stripe upon 

 the second and third rows, but as this only takes place in the most 

 dwarfed forms and is evidently due to dwarfing it can in no way be 

 taken as lesseiiing the gap between the groups that have it upon the 

 second and third, and those in which it is upon the third and fourth, 

 for it would be absurd to maintain that the former were dwarfed de- 

 scendants of the latter, since they are by no means all dwarfed forms. 



I have shown that the other traits (number of scales, color, and 

 tail length) are subject to modifying influences, and although of 

 assistance are not to be depended upon as indicating related groups. 

 If, however, I have succeded in establishing that the position of the 

 lateral stripe is not affected by the various influences that divide the 

 genus into many and diverse forms, I should find in it a trait that 

 will when availiable give us a true idea of the general relationships of 

 the difl'erent forms." 



Variation in color. — There is considerable variation in the speci- 

 mens examined, but this is so largely individual that it is difficult 

 to define a normal color for a form, and, even when there are well 

 marked geographic dift"erences among the forms, those in the same 



o Coues and Yarrow (1878, p. 273) were apparently the first to point out the signifi- 

 cance of the position of the lateral stripe, although they did not pretend that the 

 members of the different groups were genetically related. The following is their state- 

 ment of the case: "As far as we have seen, the position of the lateral stripe may be a 

 means of grouping the -species. Though this varies within certain limits, mainly 

 according to the width of the band, yet its j)osition on the third and fourth, or on X\\v 

 second and third, dorsal rows affords a ready means of distinguishing certain sets of 

 species or varieties. " The validity of this statement has been questioned by Taylor 

 (1892, 320), but, as indicated above, his criticism was proba])ly not well founded. 

 33553— Bull. 61—08 4 



