120 PROCEEDINGS OF THE ACADEMY OF [Feb., 



margin convex, basal margin straight or a little concave (as in Mar- 

 garitana margaritifera). Beaks low. No kmule. Escutcheon flat or 

 slightly concave, lanceolate, very long, extending to the posterior end 

 of the dorsal margin, bounded by acute elevated ridges. Interior white, 

 often stained with violet in the cavity, or with some faint rays of the 

 same color, or in some specimens it is delicately flesh-tinted, ochraceous 

 toward the lower margin posteriorly. There is always a broad dark 

 dorsal and posterior tract, dull violet in the cavity, but glossy blackish- 

 purple between the posterior adductor scar and the posterior margin. 

 There are three cardinal teeth, parallel to the long axis of the shell, in 

 the right valve, the anterior one much the larger; the posterior tooth 

 separated from the others, long and slender, lamellar. In the left 

 valve there are also three, the anterior one very small. There Ls a 

 short, strong lateral tooth in the right valve, a socket above it receiving 

 a small process of the other valve. 



Length 44, alt. 21, diam. 15 mm. 



Length 36, alt. 17, diam. 12.7 mm. 



Tsuda, Awa (Shikoku Is.). Types No. 88,293, A. N. S. P., from No. 

 1,622 of Mr. Hirase's collection. 



This does not seem closely related to any Trapezium I have found 

 described. There is a Cypricardia formosensis Dsh. enumerated in 

 Paetel's Catalog (III Abth., 94, 1890), without reference, which I 

 have been unable to trace. The name Trapezium is prior to the 

 equivalent terms Cypricardia Lam. and Libitina Schum. 

 Trapezium japonicum delioatum n. subsp. PI. v, fig. 44. 



Similar in contour to T. japonicum, but thinner and smaller. The 

 shell is partially covered with a very delicate corneous cuticle, decidu- 

 ous toward the beaks; dull ashen, in large part stained with violet. 

 Posterior half sculptiu-ed with delicate, subobsolete radial striae, scarcely 

 visible toward the margins except by being set with delicate, very 

 minute and short cuticular spines. Interior dark livid purplish 

 throughout, but darker at the posterior end. Lateral teeth very small. 



Length 26.2, alt. 12.3, diam. 8 mm. 



Length 24.3, alt. 12, diam. 8 mm. 



Yokohama. Types No. 69,420, A. N. S. P. 



Besides the differences given above, the escutcheon in this species 

 is usually very asymmetrical, being much narrower in the left valve, 

 where its limiting keel is nearly straight, while in T. japonicum it is 

 nearly symmetrical. 



