36 



PROCEEDINGS OF THE ACADEMY OF 



[March, 



both ends rounded , the posterior shorter and wider. Hinge very short, 

 the lateral teeth short and wide, rather near together, stout but low, 



Pisidium japonicum, lateral, posterior and interior views. 



only the anterior one projecting above the level of the valve. Cardinal 

 teeth minute, almost obsolete, narrow, very low and somewhat elongate. 



Length 2.37, alt. 2.16, diam. 1.87 mm. 



Akkeshi, Kushiro, Yesso, Types No. 94,744 A. N. S. P., from No. 

 181 of Mr. Hirase's collection. 



This is the first Pisidium to be described from Japan. It is a very 

 small species, unusually globose, with very large full beaks. 



