Fossils from the Upper Mnsashino of Kazusa and Shimosa. 167 



Cypticardia comlliophaga. Lisclike, Jap. Meeresconch., II, p. 140. 



Chama coralUopliaga. Chemnitz, Conch. Cab., X, p. 359, pi. 172, figs. 1673, 1674. 



Only a single right valve, 38 millim. in length, 19 millim. in 

 height and 6. 3 millim. in depth. It is characterized by a transversely 

 elongated, more or less rectangular or oblong form with beaks 

 near the anterior border and two main teeth accompanied hy a 

 posterior lateral. These teeth are more or less horizontal in 

 position. The radiating riblets found in living specimens are not 

 seen in the fossil, a result of friction. 



On examining the recent specimens, there is a great varia- 

 tion in shape. The younger ones are generally shorter and 

 often more oblong than the adult. 



Fossil occurrence. — Shito. 



Living. — Central and Western Japan. South Sea. Eed Sea. 

 West Indies. 



Genus THAPEZIU.W, Mühlfeldt. 



270. Tfapesiium nippouicnni, Yokoyama. 

 PI. XIII. Fig. 17. 



Shell rather thick, transversely elongated, trapezoidal, swollen, 

 very inequilateral, with anterior margin rounded, posterior trun- 

 cate, ventral somewhat excavated, postero-dorsal sloping and meeting 

 with posterior at an obtuse angle. Surface with a shallow median 

 depression, and coarsely concentrically corrugated. A rounded 

 edge runs from beak to postero-ventral corner. Area lanceolate^ 

 bounded by an elevated, rather blunt and irregular ridge on both 

 sides. Beaks large, swollen. Main teeth two in each valve, oblique; 

 posterior lateral single. 



One right and three left valves. The former measures 27.5 

 millim. in length, 18 millim. in height and 8.6 millim. in depth, 

 while the largest of the latter measures 11.2 millim. in length, 8. 1 

 millim. in height and 4.3 millim. in depth. 



Fossil occurrence. — Otake, Shito. 



Living. — Central and Western Japan. 



