IZ8 ISO 132 154 136 138 140 142 144 



Fig. 1. — The distribution of the coefficient of closeness in the Pacific Coast 



the theoretical values of the coefficients of closeness of Mollusca calculated 

 by the equation, logy = ± 0-134: {x — 35), taking the locahties north- 

 wards from lat. 35° N. on (+) side and southwards on (— ) side. The 

 values of a in the coast of the Japan Sea are difficult to decide because: 

 of less observations, but the coefficients of closeness have been calculated 

 by using the same value of a as that in the Pacific Coast, supposing no 

 difference in both coasts from the point of fact that the observed values 

 in Toyama and Hukui are nearly the same as those at the same latitude 

 in the Pacific Coast. As the points of Soya, Iturup Island, and Hukuoka 



320 



