124 Art - 6— M. Yokoyama: 



The right valve which is 8 millim. in length, 5,5 millim. in 

 height and 3 millim. in depth is subquadrate, moderately tumid, 

 and strongly inequilateral, with dorsal and ventral margins nearly 

 parallel. The posterior side is somewhat higher than the anterior, 

 with the anterior margin nearly straight, steeply sloping from the 

 beak and forming a blunt angle with the nearly straight ventral 

 margin. The posterior margin is obliquely truncate, forming 

 angles both with the dorsal and ventral margins, the angle with 

 the former being rather sharp, while that with the latter is more 

 rounded. The surface has an obtuse or flattened edge running from 

 beak to postero-ventral corner, and is ornamented with fine radia- 

 ting, somewhat sinuous striae crossed b} T distant concentric 

 laminae which are, however, mostly water-worn. Paliial sinus dis- 

 tinct, roundly triangular with apex somewhat pointed. The left 

 valve of a young shell is a little larger, being about 12 millim. long 

 and 8 millim. high. It is similarly shaped. 



Fossil occurrence in Japan. — Yokosuka Zone (Otsu and Yoko- 

 suka). 



Fossil occurrence in foreigen countries: — Red Crag of England; 

 Pliocene of Italy. 



Living. — Central Japan; Atlantic, from Mediterranean to 

 Britain. 



153. Venerupis insignis, Deshayes. 

 Pl. IX. Figs. 2,3. 



Venerupis insignis. Dkshayes, Proc. Zool. Soc. Lond., 1853, p. 6, pl. fig. 3,4. Sowerby, 

 Thesaur. Conch., II, p. 765, pl. 164, figs. 5,6. Ddnkek, Ind. Moll. Mar. Jap., p. 209. 



Sowerlry s diagnosis runs as follows: 



,, Shell irregular, strong, tumid, radiately striated, and irregu- 

 larly and concentrically subfoliated, reddish violet within, dark at 

 margin, externally golden, violet towards margin; inner margin 

 smooth. " 



We possess many specimens large and small, oblong, trapezi- 

 form, round, etc. in shape. Most of them, however, are devoid of 

 foliations by rubbing. Palliai sinus semi-elliptical, distinct. The 



