170 -^I't- 1- — M. Yokoyama : 



Fossil occurreDce. — Otakc. 

 Living. — Western Japan. 



Genus ENTOöESMA, Pliilippi. 



273. Unfoflesttui iiaviculoitles, Yokoyama. 

 PL VI. Fig. 11. 



A single left valve which is moderate in thickness, quadrately 

 oblong, much longer than high, ventricose, strongly inequilateral, 

 rounded in front, subtruncate behind. Ventral margin somewhat 

 excavated, subparallel with equally excavated dorsal margin. Beak 

 swollen. Surface much worn, apparently onl}^ with rude lines of 

 growth. Teeth absent.^ Palliai line distinct with a shallow notch. 

 Length 58 millim. Height o5 millim. Dej^th 14.6 millim. 



The shell is extremely like Entodesma navicula Ad. et E.ve. 

 (Zool. Samarang, p. 83, pi. 23, fig. 11) and E. truncal issima 

 Pilsbry (Catalogue p. 137, pi. Ill, figs. 11, 12) both of which, 

 however, are described as thin and fragile. But it is not altogether 

 impossible that this fossil may turn out to be an abnormally 

 thick-shelled form of either of the above species. 



Fossil occurrence. — Sliito. 



Family Myochamidae. 



Genus MTODOKA, Gray, 



276. Myodora fltiefitosa, Gould. 

 PL XIV. Figs. 6, 7. 



Myodora fluctuosa. Gould, Otia Conch., p. 161. Smith, Proc. Zool. Soc. London, 1880,. 

 p. 588. Brauns, Geol. Env. Tokio, p. 37. Tokunaga, Foss. Env. Tokyo, p . 39, pi. 

 II, fig. 24. Pilsbry, Catal, p. 138. 



The shell is generali}^ of a moderate thickness, though some- 

 times rather thin. It is triangular in outline, somewhat longer 

 than high, and somewhat inequilateral with the anterior side longer 

 than the posterior. Beaks small, pointed, directed backward. 

 The antero-dorsal margin is slight!}' convex and passes insensibly 

 into the rounded anterior, while the postero-dorsal is somewhat 

 concave and makes an obtuse angle with the truncate p 



