Fossils from the Upper Musashino of Kazusa and Shimosa. 159 



of concentric strise witli fine radiating lines. Lunula ovate, deep 

 and sunken. Muscular as well as palliai impressions obsolete. 



One left and two right valves. The former measures 4.7 

 millim. in length, 3.9 millim. in height, and 1.3 millim. in depth, 

 while one of the latter measures 5.3 millim. in length, 4.9 millim. 

 in height and 1.9 millim. in depth. 



Fossil occurrence. — Shito. 



Family Diplodontidœ. 



Genus I>II»I,OB>0]\TA, Broun. 



333. Diplodoiifa usfii, Gould. 

 PI. XIII. Fig. 3. 



Di^lodonta iista. Pilsbry, Catalogue, p. 133. Yamakawa, On Diplotlonia usta Glcl. 



(Japauese), Journ. Geol. Soc. Tokyo, 1909, vol. XYI, p. 482, pi. XIV, figs. 1-10. 



Yokoyama, Foss. Miura Peuin , p. 130, pi. IX, figs. 14, 15. 16. 

 Mysia {Felania) usta. Gould, Otia Conch., p. 170. 

 Mysia pacißca. Tokunaga, Foss. Env. Tokyo, p. 53. 

 Diplodonta trigonula. Brauns, Geol. Env. Tokio, p. 44, pi. VI, ffg. 25 (non D. trigonula 



Broun). 



This shell has already been described in my work above 

 cited. The specimens are very frequent, much more so than in 

 the Miura Peninsula. There is some variation in form. 



Fossil occurrence. — Otake (very frequent), Shisui (do), Ki- 

 oroshi, Tega, Shito (very frequent). Oji in Musashi. Lower 

 Musashino of Miyata. 



Living. — Northern and Central Japan. 



25S. Jfiplodonfa Japotiica, Pilsbry. 



Diplodonta japonica. Pilsbry, Catalogue, p. 132, pi. III, figs. 6, 7. Yokoyama, Foss. 

 Miura Penin., p. 131, pi. X, fig. 4. 



This shell so rare in the Lower Musashino is quite common 

 in the Upper. 



Fossil occurrence. — Otake. Kioroshi, Kamenari. Lower Mu- 

 sashino of Naganuma 



Living. — Central Japan. 



