Fossils from the Minra Penmsnlft and its Immediate North. P20 



Shell moderate in size, thin, roundly subquadrate, swollen, 

 somewhat inequilateral: anterior margin rounded, going over 

 gradually into the sloping antero-dorsal margin as well as into the 

 weakly convex ventral margin: posterior margin obliquely truncate, 

 i>v sometimes even slightly concave, forming a rounded angle with 

 the ventral margin and an obtuse one with the postero-dorsal 

 margin. Surface with a blunt keel running from beak to 

 postero-ventral corner, the space bounded by it and the posterior 

 margin being depressed in the middle, and ornamented with 

 numerous straight radiating striae crossed by tine concentric lines. 

 The other part of the surface is also sculptured with the same kind 

 of radiating striae which are not so sharp and distinct as on the 

 posterior surface. Beaks tumid, pointed. Inner margin of the 

 shell finely crenulate. The largest specimen (left valve) measures 

 about 28 millim. in length, 16 millim. in height and 10 millim. in 

 depth. A somewhat smaller right valve measures 24.5 millim. in 

 length, 23 millim. in height and 9 millim. in depth. Frequent. 



Fossil occurrence: — Koshiha Zone (Koshiba). Lower Musa- 

 shino of Kazusa. 



Living: — Central Japan. 



161. Cardium braunsi, Tokunaga. 

 Pl. X., Fig. 1. 



Cardium braunsi. Tokunaga, Foes. Env. Tokyo, p. 51, pl. HI, %. 11. 



Shell large, thick, ovately trigonal in outline, ventricose, 

 somewhat inequilateral; anterior margin rounded, posterior mar- 

 gin only little convex, forming a rounded angle with the convex 

 ventral margin. Surface radiately ribbed; ribs twenty-three to 

 twenty-six, elevated, nearly flat-topped, quadrate in cross-section, 

 separated by interspaces more or less narrower than the ribs them- 

 selves. Incremental lines distinct, making the ribs appear some- 

 what telescopic. 



A single specimen of a left valve lacking the posterior half. 

 It is 67 millim. high. 29 millim. deep and about 70 millim. 

 long and exactly agrees with the species first described by Toku- 



