42 BULLETIN Gl, UNITED STATES NATIONAL MUSEUM. 



In the discussion of the vahie of the characters an attempt was made 

 to show that the position of the lateral stripe groups related forms, 

 and that the proportionate tail-length, and the number of preoculars 

 and presence or absence of lateral cross-bars,'^ are also of value in this 

 regard, if used within the limits of the groups having the lateral stripe 

 in the same position. If we have made our point, then, the nineteen 

 forms defined in this table fall naturally into four groups, the members 

 of which should be genetically related. 



To each of these four groups of garter-snakes we have for conveni- 

 ence given the name of the best known form which it includes. Thus 

 we have the Radix group with the lateral stripe upon the third and 

 fourth scale rows and a short tail ; the Sauritus group with the lateral 

 stripe on the third and fourth rows and with a long tail; the Elegans 

 group with the lateral stripe upon the second and third rows, and with 

 either more than one preocular scute in some part of the range or the 

 lateral spots arranged as cross-bars in some part of the range, and 

 the Sirtalis group with the lateral stripe on the second and third rows, 

 and never more than a single preocular, or lateral cross-bars. 



It will probably be conceded at once that the ribbon-snake group 

 (Sauritus) is a natural one, and there can be little question that the 

 forms included in the Radix group are also related, although the 

 placing of marcianus with these snakes will be seriously questioned 

 by some herpetologists. In the case of the other groups, Elegans 

 and Sirtalis, the affinities are in many cases much less obvious, but 

 it can not be denied that as thus defined the groups include those 

 forms which are evidently related. Thus there is no question but 

 that hammondi, ordinoides, and elegans, which are here placed in the 

 Elegans group, are closely related, nor that sirtalis, parietalis, and 

 concinnus, in the Sirtalis group, actuall}^ intergrade. The evidence 

 for the inclusion of the other forms in these groups, as well as further 

 proof that the above-mentioned forms are properly placed together, 

 will be given in more detail when the forms are discussed separately, 

 and the lines of interrelationship considered. 



The continuous geographic range of the four groups also seems to 

 strengthen the evidence of the characters that they are associations 

 of directly related forms. As is shown on the maps, the Radix group 

 occurs on the Mexican plateau, great plains, and in the prairie region; 

 Sauritus is a coastal plains group, extending from British Honduras 

 to Maine, only penetrating into the interior in the forests of eastern 

 United States and along the streams of the great plains ; the Elegans 

 group occupies the Mexican plateau and, in the United States, all of 



« It has been a source of regret to the writer that a single trait could not be found to 

 separate the Elegans and Sirtalis groups. Most students of snakes have encountered 

 a similar difliculty, however, for the different groups of snakes, apparently t)wing to 

 the recency of the order, are frequently not sharply defined by any single difference 

 that is obvious. 



