220 ^ r t- 6.— M. Yokoyama : 



ly in a broken state. Of the three main teeth, the middle and 

 the anterior in the left valve are bifid. 



Fossil occurrence: — Yokosuka Zone (Otsu); Upper Musashino 

 of Musashi. 



Living: — Northern (Rikuzen), Central and Western Japan; 

 Formosa, China Sea; Coast of Cochin China. 



Genus Meretriac, Lamarck. 



147. Meretrix (Callista) chinensis, (Chemnitz;. 



Pl. VIII. Figs. 9,10. 



MiTctrix (Callista) chinensis. Piesbry, Cat. Mar. Moll. Jap., p. 127. 



Cyiherea chinensis. Pfeiffer in Syst. Conch. Cal. Mort. Cheinn. vol. XI, pt. I, p. 31, pl. 

 XI, fig. 2. Lischke, Jap. Meeresconch., I, p. 122. Tokunaga, Foss. Env. Tokyo, p. 46, pl. 



in, fig. 4. 



Callista chinensis. Dünker, Index Moll., p., 200. 

 Venus eh\nensis. Chemnitz, Conch. Cab., XT, p, 217, pl. 202, fig. 1976. 



Venus pacifica. Dielwyn, Catal. I, p. 175, no. 40. Schrenck, Moll. Aoiurl. u. 2. nordjap. 

 meeres, p. 541. 



Only a young right valve and two fragments of a grown shell 

 which, on comparison with the recent specimens, have proved to 

 belong to the above mentioned species. 



Fossil occurrence. — Naganuma Zone (Naganuma). Upper 

 Musashino of Musashi, Shimosa and Kazusa. 



Living. — Northern, Central and Western Japan; China Sea; 

 Australia. 



Genus Venus, Linne. 



148. Venus jedoensis, Lischke. 



Pl. VIII. Figs. 11,12. 



Venus jedoensis. Ltschke, Jap. Meeresconch., vol. Ill, p. 84, pl. VII, fige. 1-9. Dünk kr, 

 Index Moll., p. 196. 



Man}' specimens both young and lull grown. In the young 

 forms the outline of the shell is more or less elliptical, while in the 

 older ones it is more subquadrate, owing to the subtruncation of 

 the posterior end. The largest specimen which we possess is a 

 left valve, 59 millim. in length, 49 millim. in height and about 



