158 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.46. 



Range of variation in 44 specimens .' 199-232 



Range in 9 mainland specimens 199-214 



Arithmetical mean 208 



Range in 35 island ppecimens 208-232 



Arithmetical mean 221 



Overiapping of mainland and island specimens: 



In terms of shields 7 



In percentage of the total range 21 



A more instmetive graphic scheme will result if the records of each 

 specimen be plotted on squared paper, due regard being taken of the 

 gastrostege and urostege count. 



Diagram showing the variation in the subcaudah. 





Range of variation in 43 specimens: 



Ventrals 141-152 



Subcaudals 55-83 



Range in 9 mainland specimens: 



Ventrals 144-151 



Subcaudals 55- 65 



Range in 34 island specimens: 



Ventrals 141-152 



Subcaudals 63- 83 



Overlapping of mainland and island specimens: — 



Ventrals (range 12, overlapping 8) per cent. . 66. 6 



Subcaudals (range 29, overlapping 3) do 10. 3 



The variation in the number of dorsal vertebrae, as evidenced by 

 the gastrostege count, is seemingh^ of no consequence. As to the 

 caudal vertebrae, however, it is most apparent that the specimens 

 from the two geographical regions are in this respect quite distinct. 

 Furthermore, owing to the fact that a straightforward species is 

 under consideration, occasional intermediates between the two groups 

 exist. 



