A. ('. Dl.MON 



41 



<'. ( 'on-clutiun lictwcci] lciiu;tli and ratin i>r (liaiiictor to length nf sliclln of jV. tricittala froiii 

 locality 3. 



Diameter 

 Leiigth : Loiigtli 



Moan = 7-9(;29. ^[can = 6-3ir)8. 



Standard I)cviation = 2-() 12. Standard Deviation = 1-870. 



(.'orrelati(in= - '"lOS. 

 Total froqnoiK'y = 456. 



Indc.K 



f. Correlation between Icngth and ajiical angio of sliells of N. trivittata from locality 3. 



Length : Anglo : 



Mean = 7-695. Mcan = 5-722. 



Standard Deviation = 2-590. Standard Deviation = 2-047. 



Correlation = — -6577. 

 Total frequency = 461. 



Angle 



■a 



Biometrika ii 



