ON JAPANESE SPECIES OF COKBICULA. 



159 



Corbicula awajiensis Pilsbry. Tlate VII, fig. 13, 14. 

 Avvaji Island. 



Corbicula nipponcnsis n. sp. Plate VII., fig. 3, 4. 



Shell rounded-oval, with moderately elevated beaks ; oliveaceous 

 with chestnut or blackish concentric streaks or zones, or mainly black 

 with some lighter zones, the posterior slope usually black. Surface glossy 

 as though varnished ; rather finely striated, but often irregularly so. 

 Lunule defined by a narrow raised line. Dorsal slopes of the valves 

 convex, ends rounded, the posterior end slightly more produced. Hinge 

 strong, the nymphs wide and only very minutely roughened. Cardinal 

 teeth diverging, the middle one subvertical in the right valve, oblique but 

 not parallel to the posterior lateral in the left valve. The anterior lateral 

 tooth in the left valve is well separated from the adjacent cardinal by a 

 deep notch. Interior violet whitish, usually with a dark violet band along 

 the basal margin. 



Length 40I, alt. 37, diam. 23 mm. 



Kogawaranuma, Mutsu. 



C. nipponeiisis is chiefly characterized by its wide, smoothish 

 nymphs, distinct, smooth lunule, fine striation, and by having the lateral 

 teeth usually not curved at the ends by the encroachment of the posterior 

 adductor muscle. It is closely related to C. sadocnsis, but that is longer 

 and less triangular, with shallower beak cavities, and the hinge-line forms 

 a lower arch. C. sadocnsis is evidently an insular modification of the 

 widely distribu'ed C. nipponeiisis. 



The type lot of C. nipponcnsis consists of remarkably beautiful shells 

 with a varnish-like gloss. In another lot from Mutsu at Jusangata (Jusan- 

 mura), the shell is black, less lustrous, and smaller, length 34^, alt. 30I, 

 diam. 19 mm.; the striation is very distinct, and there is usually a purple 

 stain in the cavity of the beaks, which is not present in the type lot. 



Other shells from Shariki-mura, Mutsu, are similar to the preceding or 

 larger ; length 38, alt. 35, diam. 23 mm. 



