VARIATIONS OF GARTER-SNAKES. 33 



lanogaster, angustirostris , hammondi, ordinoides, and elegans) either 

 quite constantly or in some part of their range, exhibit more than one 

 preocular. Whatever may be the cause of this division of the pre- 

 ocular, other evidence, as will be shown later, appears to indicate 

 plainly that these forms are closely related, so that the presence of 

 two or more preoculars over all or a part of the range separates 

 them from all others in the genus. 



Although the arrangement of the lateral spots are usually referred 

 to in descriptions, the character is entirely too variable to be used 

 extensively in diagnoses. As before stated, when distinct they are in 

 the form of two rows of alternating spots on either side between the 

 stripes. In forms where they are ordinarily distinct, however, they 

 may be fused to a variable extent in melanic individuals, while being 

 more than usually prominent in light-colored ones. While they are 

 thus quite variable individually, they also exhibit some racial differ- 

 ences. Thus, in parietalis the upper row is usually fused into a band,, 

 and in eques, sirtaJis, and parietalis the first few anteriorly frequently 

 tend to fuse with their neighbors in the opposite row to form cross- 

 bars. In two forms the arrangement has become modified into a 

 series of transverse blotches that usually in one form (scalaris) stop 

 at the dorsal stripe but in another (phenax) crosses the back and 

 fuses with its fellow on the opposite side, forming crossbars. As 

 in the case of the number of preoculars, not enough is known 

 about the factors which influence the arrangement of these spots to 

 enable us to pin our faith to them as indicative of racial affinities; as 

 also with the number of preoculars, however, the fusion of the spots 

 into transverse blotches for the entire length occurs in forms which 

 other evidence seems to indicate are closely related, so that the 

 presence of this arrangement seems to group these forms in a natural 

 way. Furthermore, I believe (my reasons are given on pp. 120-158) 

 that the forms that have this arrangement of the lateral spots are 

 directly related to those that tend to have more than a single pre- 

 ocular, in which case the two characters when used together serve 

 to define a natural section of the genus. 



Variation in strip>es. — Ever since the establishment of the genus 

 Eutaenia by Baird and Girard, the possession of three longitudinal 

 light color bands has been considered a distinctive feature of the genus 

 and the particularities of these stripes used as diagnostic characters. 

 They are, as we have seen, disposed as a single dorsal and two lateral 

 bands, the dorsal covering the median and usually more or less of the 

 adjacent rows, when present, the laterals a varying amount of the 

 second, third, and fourth rows on either side. 



The peculiarities of the dorsal stripe that have been used in sys- 

 tematic work are its presence or absence and width, and these char- 



