Fossils from the MLuni Peninsula and its Immediate North. ];-}^ 



fossil specimens from the Upper Musashino of the vicinity of Tokyo 

 found it to be 100 to 87-100. It is the merit of this lamented 

 palaeoconchologist in pointing out the errors committed both by 

 JBrauns and Tokunaga in naming this species Diplodonta trigomila 

 Bronx and 3fysia pacifica n. sp. respectively. 



Frequent. 



Fossil occurrence. — Miyata Zone (Kami-Miyata and Nagai); 

 Upper Musashino of Musashi and Shimosa. 



Living. — Northern and Central Japan (Hitachi). 



163. Diplodonta semiaspsra, (Philippi). 

 Pl. X. Figs. 2,3. 



Diplodonta semiaspera. Philippi, Archiv für Naturg., I, 1836, p. 225, pl. VII, fig. 2. Ddk- 

 kke, Index Moll., p. 218. 



The shell is thin, swollen, slightly inequilateral, roundly 

 ovate in outline, anterior side narrowed and obtusely ending, the 

 posterior margin broadly rounded. Surface only with unequal 

 concentric lines of growth. Beaks small and pointed. Muscular 

 impressions pear-shaped, often tolerably elongated. 



The largest specimen (left valve) in our possession measures 

 18 millim. in length, 16 millim. in height and 9 millim. in depth. 

 Aright valve of a living shell from A wa (Bôshû) measures 21,5 

 millim. in length, 17,5 millim in height and 9,5 millim in depth. 



Rare. 



Fossil occurrence. — Miyata Zone (Shimo -Miyata); Koshiba 

 Zone, (Koshiba). Upper Musashino of Musashi, Shimosa and 

 Kazusa. 



Living. — Central and Western Japan; West Indies; Mazatlan; 

 Patagonia. 



164. Diplodonta japonica, Pilsbry. 

 Pl. X. Fig. 4. 



Diflodonta japonica. Pilsbky, Cat. Mar. Moll. Japan, p. 132, pl. Ill, figs. 6,7. 



A single left valve, 17,5 millim. long, 15,5 millim. high and 

 7 millim. deep. 



