10g Art. 6. —M. ï'okoyama : 



Very frequent. 



Fossil occurrence. — Miyata zone (Shimo-Miyata, Yaniagayado 

 in Kami- Miyata, Motowada and Nagai); Yokosuka Zone (Ota* 

 andYokoska); Koshiba Zone (Kosbiba); Naganuma Zone (Naga- 

 numa): upper Musashino of Musashi, Kazusa and Shimosa. 



Living. — Northern Japan (the Hokkaido),* 



Genus Mi aster otitic Mayer. 



129. Basterotia gouldii (A. Adams). 



Pl. VII. Fig. 7. 



Basterotia gouldi. Pilsbkt, Cat Mar. Moll. Japan, p. 118. 



Eucharis gouldii. A. Adams, Ann. Mag. Nat. Hist., April, 1864, p. 309, November 1868, 

 p. 366. DutfKER, Index Moll. Map. Jap., p. 178, pl. IX. figs. 7-11. 



Shell ovately subtrigonal, convex, rugosely concentrically 

 striate, subgranose in front. Beaks tumid, strongly, inclined for- 

 ward, with an obtuse keel running from the beak to the postero- 

 ventral angle. Right valve with one strong tooth and a liganiental 

 pit behind it. 



A single right valve 8,5 millim. long and 7,5 millim. high. 



Fossil occurrence. — Yokosuka Zone (Otsu). 



Living. — Western Japan (Setouchi, Kyushu). 



130. Basterotia trapezium, Yokotama. 

 Pl. VII. Figs. 8, 9. 



Shell rather thin, moderately swollen, strongly inequilateral, 

 roundly four-sided, no two sides of which are equal or parallel, 

 narrowed towards front and rounded at margin, dilated behind 

 and obliquely truncate, so that the posterior margin forms a 

 rounded angle with the broadly arcuate ventral margin. Surface 

 concentricatly rugose, a keel which may be rather indistinct run- 

 ning from the beak to the postero-ventral angle. Beaks small, 

 pointed. 



* Tokunaga mentions Whampoa nt'ar Canton as one of the places where Corbula venusta 

 lives. But this seems to he a mistake. 



