1913.] NATURAL SCIENCES OF PHILADELPHIA. 513 



Sum of the gastrosteges and urosteges: 



Range in 17 specimens. 210-274 



Range in 12 from mainland 210-250 



Range in 5 from Formosa „ 200-274 



Gap between mainland and island specimens: 



In terms of gastrosteges 4 



In percentage of range ; 6i% 



If this data be plotted on squared paper, due regard being taken of 

 the gastrostege and the urostege count, an instructive diagram will 

 result. The solid dots represent mainland and the circles island 

 specimens; where the sex has been recorded there is added the con- 

 ventional sign. 



Observations along these lines are of interest when carried out as 

 studies in geographical variation, but when thej^ become the basis of 

 new species nothing but confusion will eventually result. 



The point that these tables really make clear is that the island 

 specimens differ from those of the mainland in having an increased 

 number of vertebrae. This is a well-known phenomenon, and it occurs 

 in almost all the species of Colubrinse, Najidse, and Crotalinae that 

 inhabit both the mainland of Asia and the adjacent island arcs. 



To estal^lish C. swinhoei involved the following procedure: From 

 the records of twelve mainland and five island specimens, seventeen 

 in all, certain additions and subtractions were made, and a difference 

 of four vertebrae in a range of sixty-four, equivalent to Gj%, was 

 discovered. This Gj% variation in a single character was added to 

 the locality label, and the sum was a new species. 



Where the same species inhabits the mainland and an adjacent 



