VARIATIONS OF GAETER-SNAKES. 157 



or Elegans groups. I believe that I have proven conclusively in the 

 discussion of the two forms that ordinoides and elegans are not only 

 closely related but that they actually intergrade. Tliis relationship 

 has been more or less recognized as far as the California (elegans) 

 section of the former is concerned for a considerable number of 

 years, but the Oregon and Washington section has often been con- 

 sidered as a distinct species. To class this part of the form with sir- 

 talis, as has been done several times, for the reason that the two 

 forms agree in having 19 scale rows and 7 supralabials, is absurd. In 

 the first place, the recognized meTYibers of the Sirtalis group in this 

 part of North America never have more nor less tlian 19-17 scale rows, 

 7 supralabials and one preocular, while ordinoides exhibits both more 

 and less than this number of scale rows, and frequently more tlmn one 

 preocular, so that, while the latter is evidently a dwarfed offshoot of 

 some form, the parent stoclc must have been one with more than 19-17 

 scale rows and 7 supralabials. In the second place, an undoubted 

 form of the Sirtalis group occupies almost exactly the same region 

 and probably also the same habitat as ordinoides, which opposes the 

 evidence of a closer relationship between ordinoides and the Sirtalis 

 group. 



Its affinity with elegans, on the other hand, is shown by the fact 

 that the scutellation and color pattern of ordinoides becomes practi- 

 cally identical with elegans as the range of the latter is approached, 

 the similarity in the scutellation being brought about by an increase 

 in the number of scales in the dorsal, labial, ventral, and subcaudal 

 series, and by the occasional presence of two preoculars. The resem- 

 blance expressed by the similarity in these traits becomes so close 

 in the intermediate region that specimens can not be referred exactly 

 to either form. We believe the conclusion is unavoiclable, therefore, 

 that ordinoides represents the geograpliic extreme of the Elegans 

 group in North America. If this is true it is interesting to note that 

 it is by far the most dwarfed form among the North American mem- 

 bers of the group. 



CONCLUSION. 



If it be granted from the evidence produced above that angusti- 

 rostris, melanogaster , scalaris, phenax, hammondi, elegans, and ordi- 

 noides form a group of genetically related forms (fig. 69), this group 

 is very similar to the Radix and Sauritus groups above described in 

 that (1) the form with the largest scutellation occurs on the northern 

 part of the Mexican plateau; (2) both to the north and south of this 

 center of maximum scutellation a decrease in the number of scales 

 in each series takes place; (3) in North America the group enters a 

 region that is without effective physical barriers to its northward 

 extension and extends as far to the northward as the increasing 



