158 



HENRY A. P1LSBRV. 



Corbicula viola n. sp. Piate VII, fig. 7, 8, 9, 10. 



The shell is ovate or triangular-oval in outline, rather coarsely sculp- 

 tured with narrow riblets which are rather widely spaced. On the 

 posterior slope the riblets disappear, giving place to a dull, somewhat 

 lamellose cuticle, but elsewhere the surface has a varnish-like gloss. It is 

 yellow with brown concentric streaks, or in older shells, brownish-black 

 with some light streaks. The anterior end is broadly rounded, the dorsal 

 border highly arched, with rather prominent beaks, the slopes slightly 

 convex ; the posterior end is narrower and more lengthened than the 

 anterior. 



The interior is dark violet below the palliai line, lighter or whitish- 

 violet in the cavity. In the right valve both cardinal teeth are oblique, 

 nearly parallel with the posterior lateral tooth. In the left valve the anterior 

 lateral is separated by a deep notch from the adjacent cardinal tooth. 

 The narrow nymphs are only very minutely roughened. 



Length 27, alt. 23.3, diam. 15 mm. 



Chikumanaiko, Lake Biwa. Types collected by Mr. T. Iwakawa. 



This seems from the material at hand to be a distinct species, differ- 

 ing from C. japon ica and C. sandai by the development of ribs over the 

 whole median portion of the valves, and from C. nipponcnsis by the coarse 

 sculpture and more oblique cardinal teeth. It differs more fundamentally 

 from C. Icana and its immediate allies by the much less coarsely 

 roughened nymphs. 



C. viola is rather a small mussel, and those received have a dingy 

 exterior until cleaned, being thinly covered with a ferrous deposit. 



Corbicula sadoensis Pilsbiy. Plate VII, fig. 15, 16. 



Proc. Acad. Nat. Sci. Phila. 1901, p. 406 (Sado). 



Sado Island (Hirase) ; Kahokugata, Kaga (Iwakawa). Closely related 

 to C. nipponcnsis, but longer and less high, with the hinge margin much 

 less curved. 



