Fossils froui the Upper Musashiiio of Kazusa and Shimosa. 149 



end wliich is bluntly pointed. Of the three main teeth, tlie middle 

 in the left 'valve and the middle and the posterior in the right are 



bifid. 



The young specimens of tliis species are more rounded in out- 

 line than the adult. 



Fossil occurrence.— Otake (not rare), Kioroshi, Tega. Lower 

 Musasliino of Miyata and Yokosuka. 



Living. — Northern, Central and Western Japan. 



2.11. FeMifs neasfarfoifles, Yokoyaina. 

 PI. XI. Figs. 9, 10. 



Shell small, thick, ratlier compressed, triangular. Anterior 

 side only a little longer than posterior. Anterior end sharply 

 rounded. Antero-dorsal margin nearly straight, sloping. Postero- 

 dorsal and posterior margins together forming a broad curve. 

 Postero-ventral corner obtusely angulate. Surface smooth, only 

 with lines of growth. Beaks small, pointed, curved in. Teeth 

 three in each valve with the middle one thickest. No lunula. 

 Liner margin smooth. Palliai sinus shallow, triangular, blunt at 

 end. The largest right valve measures 20.3 millim. in length, 15.6 

 millim. in height and 5 miUim. in depth, while the largest left 

 measures 19.4 millim, in length, 14. G millim. in lieight and 4.3 

 millim. in depth. 



The compressed state of tliis shell reminds us of the genus 

 Asktrte, but as the name astartoides is already used ])y P>eck, 

 neadartoides was chosen as the specific name. 



Fossil occurrence. — Otake (frequent), Kainenari (do), Tega 

 (do), Kioroshi (most frequent), Shito (rare). 



Living. — Central Japan. 



Genus CHI OK E, Megerle von MüMfeldt. 



233. Chione isahellina, (Philippi). 



Chionr, isahellina. Desliayes, Couch. Brit. Mas., I, p. 124, no. 17. Danker, Index Moll,, 

 p. 198. Yokoyaina, Foss. Miura Penin., p. 121, pi. VIII, fig. 13. 



