156 



HENRY A. P1LSBKV. 



From Lake Suwa, Shinano, a series of peculiar shells was collected, 

 measuring only iS to 22 mm. long, the outside pale greenish yellow, the 

 interior whitish in the cavity, pale purple below the palliai line. These 

 shells agree with C. Icana in sculpture etc., but differ in the color inside, all 

 other Icona, I have seen being violet. 



Although it is widely distributed, I have not seen this or any other 

 Corbicula from Yesso. 



I have not seen specimens of C. straminea Reinh. from Hakone 

 Lake, the type locality, but I cannot see, from the description and figures, 

 that it diners materially from the young of C. Icana. This question may 

 be taken up again when a collection is made at Hakone. 



Corbicula orthodonta n. sp. Plate VII, fig. i, 2. 



The shell is somewhat triangular, the upper margins sloping steeply 

 and straight on each side of the high beaks, the basal margin evenly 

 arcuate. The anterior end is broadly rounded, the posterior end narrower 

 and somewhat lengthened. The glossy surface is sculptured with rather 

 closely set ribs, slightly narrower than the intervals, and about one 

 millimeter from crest to crest in the middle of the valve. In old shells the 

 ribs are obsolete near the basal margin. The coloris greenish-yellow with 

 wide blackish zones, old shells being mainly black. The interior is 

 lusterless, violet-tinted white. The hinge is rather narrow. Nymphs 

 narrow and strongly roughened. In the right valve the posterior cardinal 

 tooth is parallel to and in line with the posterior lateral, but the posterior 

 edge of the anterior cardinal tooth points towards the middle of the basal 

 margin. In the left valve the upper end of the anterior lateral tooth is 

 separated from the adjacent cardinal tooth by a deep furrow. The muscle 

 impressions are small but distinct. 



Length 4S, height 42.5, diam. 25.5 mm. 

 46, „ 40.5, 24.5 „ 



I [abitat, Owari. 



The unusually straight slopes of the dorsal borders of the valves, on 

 both sides of the rather small but high beaks give this mussel a some- 



