146 A.rt. 6.— M. Yokoyania: 



Family Anomiidae. 



Genus Anomia, LiNNÉ. 



185. Anomia cytaeum, Gray. 



Pl. XI. Fig. 17. 



Anomia cytcicum. Gbat, Proc. Zool. Soc. London, 1849, p. 115. Beeve, Conch. Icon., vol. 

 XI, Anomia, pl. II, fig. 10 ab. Schbenck, Nordjap. Moll., p. 473. 



A few examples among which there is one with both valves 

 complete. It is nearly orbicular in shape, strongly compressed, 

 22 millim. high and 24 millim. long. The surface is very uneven 

 especially in the upper valve on which we see irregular wrinkles 

 and tubercles in some places. The concentric lines of growth are 

 undulating and sublamellar. The foramen is very large, oval, 9 

 millim. high and 6 millim. long. Compared with the living 

 forms the hinge-line is more curved. The radiating ribs as 

 shown in Reeve's figure are hardly to be seen, a character also 

 observable in recent specimens from Hakodate. 



Fossil occurrence. — Miyata Zone (Shimo-Miyata, Kami-Miya- 

 ta and Motowada); Yokosuka Zone (Yokosuka and Otsu); Koshi- 

 ba Zone (Koshiba); Naganuma Zone (Naganuma). 



Living. — Northern and Central Japan; China (Mouth of the 

 Yangtsekiang). 



186. Anomia nipponensis, Yokoyama. 

 Pl. XI. Figs. 18, 19. 



Several example? which, however, all belong to the upper 

 valve. 



The shell is thin to moderately thick, suborbicular to some- 

 what obliquely ovate in form. The upper valve is strongly 

 convex with the surface radiately ribbed. The ribs are mostly 

 close together and numerous, unequal, irregular, somewhat 

 undulating and looking more like wrinkles than ribs, and often 

 indistinct or obsolete near the beak. The incremental lines are 

 numerous and distinct, and on crossing the ribs they make the 

 latter appear often striated. In some specimens these lines of 

 growth show a tendency to assume a sublamellated character. 



