Fossils from the Miura Peninsula and its [immediate North. [39 



Zone (Naganuma). Miocene of Poronai (very numerous). Upper 

 Musashino of Shimosa and Kazusa. 



Living. — ('entrai and Western Japan. 



175. Venericardia ferruginea, Adams. 

 Pl. XI. Figs. 3, 4. 



Cardita ferruginea. Clessin in Syst. Conch. Cab. Mart. Cheinn., vol. X, pt. 1. j>, 17, pl. 6, 

 rig. 11. Pilsbry, Catalogue p. 135. 



Cardita rotundi. Tokunaga, Foss. Env. Tokyo, p. 55, pl. III. rig. 17. 



Shell small, ovate to roundly trigonal in outline, thick, mode- 

 rately tumid, very inequilateral; anterior as well as posterior mar- 

 gin rounded, the former more narrowly than the latter; ventral 

 margin broadly arcuate, or even almost straight, in which latter 

 case the postero-ventral corner is more or less subangulate. The 

 surface is ornamented with about twenty radiating ribs separated by 

 much narrower interspaces. These ribs are rounded, hut some- 

 what flattened toward the ventral margin and made more or less 

 nodose by concentric impressed lines. Beaks prominent, pointed. 

 Lunula very small, hut deep and cordate. Hinge-teeth two; the 

 anterior in the left valve is very short, while that of the right, 

 valve is large and obliquely triangular; the posterior tooth elon- 

 gated, especially in the left valve. Inner margin crenate. 



The shell is very variable in shape and thickness. The length 

 may be equal to the height, or a little greater. The thickness 

 varies from 6 to 8, if we take the length for 10. The largest speci- 

 mens of both fossil and recent shells in our possession measure 

 about 19 millim. in length. 



Tokunaga described this specices as new, giving its more 

 rounded shape, more prominent umbones and less thickness as its 

 distinguishing characters. But hundreds of fossil specimens which 

 we possess show all grades of differences in shape 



Very frequent, especially at Kami-Miyata. 



Fossil occurrence. — Miyata Zone (Mukaibatake in Shimo- 

 Miyata, Yamagayado and Jwaiguchi in Kami-Miyata. Motowada 

 and a place simply labeled Kami-Miyata); Yokosuka /on.' 

 (Isemachi, east of Otsu); Kanazawa Zone (Kanazawa); Koshiba 



