Fossils form thé Mium Pettinteula an)d its [inmediate North. 173 



to the two sides of a triangle having its apex in common with that 

 of the whole pit Beaks very small and pointed. Inner margin 

 smooth and sharp. 



There is a considérai >le variation in shape and thickness. The 

 shape, however, is in general oblong, though, in a specimen which 

 I formerly called var. elowjata (the figure is in the above cited 

 journal), it is posteriorly somewhat pointed. Between these two 

 forms, there are all sorts of gradations. If we consider the shell as 

 an ellipse whose longer diameter is 10, then the shorter diameter 

 varies between 8 and 7, 6. The thickness of a complete shell is 

 about one-half the longer diameter. 



The largest specimen in our collection is about 30 millim. in 

 its longer diameter. 



This species shows a great resemblance to Limopsis marionensis 

 Smith (Challenger Lamellibranchiata, p. 254, pi. XVIII, figs. 2, 

 2b) from the Indian Ocean; but the Japanese form has the anterior 

 side below the hinge invariably a little more produced than 

 Smith's. Limopsis pelagica Smith described in the same work as 

 occurring in Japan is also closely related to ours, but the beak is 

 more prominent, the shell less oblique and the posterior wing 

 more conspicuous. 



Very frequent, especially at Koshiba, Nojima and Kikkosan. 



Fossil occurrence. — Miyata Zone (Jinyaato in Kami-Miyata); 

 Kamakura Zone (between Urago and Enokido); Kanazawa Zone 

 (Kanazawa and Nojima); Koshiba Zone (Koshiba and Of una); 

 Naganuma Zone (Kikkôsan and Naganuma). 



Living. — Central Japan (rarely found near the coast of 

 Bôshù). 



223. Limopsis crenata, A. Adams. 

 Pl. XVIII. Figs, 17, 18. 



Limopsis ennata. A. Adams, Descrip. Some Species Limopsis fr. Cumingian Collection, 

 Proc. Zool. Soc, London, 1862, p. 230. Tokoyama, Species of Limopsis found in the Neogene 

 of Koshiba, Jour. Geol. Soc. Tokyo, vol. XVII, no. 205, Oct, 1980, p. 3, pl. IX. figs. 8-11. 



Shell small, rather thin, convex, oblique, roundly ovate to 

 oblong, nearly as high as long, anterior margin rounded, posterior 



