182 



UNIONID^. 



Anodon "undulata. 



Fig. 79. 



Shell transversely ovate, rather thick, beaks prominent, epidermis dark-brown, 

 radiated, coarsely wrinkled ; hinge-margin undulated, and with the vestige of a 

 tooth. 



Anodonta undulata, Say, Nicholson's Encyc. Amer, ed. iv. pi. 3, fig. 6. — Lea, Synops. 



Naiad 50. 

 Anodon nigosus, Swainson, Zoill. Illust. pi. 96. 

 Anodon undulata, Gould, Inv. 120, fig. 79. 



Shell oblong-ovate, thick and strong ; beaks sub-central, ele- 

 vated, the points in contact, and when not eroded they exhibit four 



or five small undula- 

 '^' ■ tions upon them ; be- 



fore them is a spear- 

 shaped pit or areola, 

 not covered by the ep- 

 idermis ; behind them 

 the margin is slightly 

 compressed, and has 

 two or three coarse, 

 sub-marginal furrows ; 

 no distinct angle at 

 the termination of the 

 ligament ; posterior end somewhat bluntly rounded ; anterior end 

 compressed, sharply rounded ; basal margin regularly curved ; e|)i- 

 dermis dark-brown, radiated in most specimens, smooth, and closely 

 adhering towards the beaks, but lying in numerous, rather loose 

 folds near the margin ; interior inclined to salmon-color, and gran- 

 ulated centrally, bluish-white outside of the pallial impression, with 

 a broad margin of olive-color. Hinge-margin waved under the 

 beaks, compressed on the right valve so as to form something like 

 an elongated cardinal tooth, which is received into a corresponding 

 recess in the left valve. Length, three and one half inches ; height, 

 two inches ; breadth, one and one half inches. 



Found in the Blackstone River and its tributaries, of large size 

 and great perfection. 



It is impossible to lie certain that this is A. undulata of Say, on 

 account of the small size of the specimen he described ; but it 

 seems to be the shell which Mr. Lea regards as such. It seems to 

 be a different thing from the shell described by Hildreth under that 



A. undulata. 



