VARIATIONS OF GARTER-SNAKES. 69 



other hand, the number of dorsal scale rows, subcaudals, and ven- 

 trals are apparently less. Thus there are no serious objections to 

 deriving Tnarcianus from megalops on structural grounds (the geo- 

 graphic probilities will be considered later), but still there is no satis- 

 factory proof that such a relationship actually exists, and we must 

 look elsewhere for evidence of its relation to the Radix group. 



On the north inarcianus meets radix, and when the scutellation of 

 these forms is examined it is seen that there is no great break between 

 the forms in this regard. The number of scale rows and labials are 

 the same near the common boundary, and, notwithstanding the fact 

 that marcianus has a smaller range of variation in the number of 

 ventrals (157-163) as compared to radix, 159-172, in the same general 

 region, the averages are very close, while the tail length and number of 

 subcaudals are approximately the same. In spite of the fact that the 

 color of radix is usually darker, the general pattern is very similar to 

 that of marcianus. Indeed, in western specimens of radix the ground 

 color becomes quite light, so that in the case of two specimens from 

 Oklahoma, in the possession of the Field Museum (Nos. 630, 631), it 

 is impossible to tell whether they are to be referred to radix or mnr- 

 cianus. In these specimens the color is dark brownish yellow, the 

 first and second rows light ash. The spots are in three very distinct, 

 alternating rows on the skin and all of the involved scales; the first 

 row being on the first and second rows, the other two between the 

 stripes. The lateral stripe is distinct, narrow, and anteriorly on the 

 third and part of the fourth rows, posteriorly on the second and third. 

 Anteriorly the spots tend to fuse into large blotches. Eye rather 

 small. Head dark olive. The first, second, seventh, and eighth 

 supralabials are more olive, the third to sixth, inclusive, being light 

 yellow; all are margined with black, the fourth, fifth, and sixth the 

 heaviest. This coloration is so like that which exists generally in 

 marcianus as to make it evident that these specimens are closer to 

 this form than any other. The points that indicate an affinity with 

 radix are the fact that the first and second rows of scales differ in 

 color from the lateral stripe and are covered by the first row of spots, 

 and that the lateral stripe seems to be partly on the fourth row. If 

 I am right in considering that these specimens from Oklahoma 

 indicate, that marciajius and radix are directly related, the lateral 

 stripe in the former must be considered as belonging on the third and 

 fourth rows of scales, which throws the form with the Radix group. 



Whether marcianus and radix intergrade at the present time along 

 their common boundary, or not, is not a question to be decided on the 

 basis of two specimens, but, be this as it may, it must, we think, be 

 conceded that there is such a very close similarity in scutellation and 

 color between the two forms as to warrant the conclusion that they 

 are directly related, while if we consider the lateral stripe in the former 

 3:^553— Bull. 61—08 6 



