UNio. 169 



color ; but I have a series of a strongly marked variety from the 

 Shawslieen River in Andover, where the color is dark chestnut with 

 considerable lustre, the young shells are radiated with dark lines 

 almost as much as U. radiatus, and some of the old shells are very 

 coarsely plaited from the beaks downwards into parallel folds. 



Tlie only New England species with which this is lial)le to be 

 confounded are U. nasutus and U. radiatus. The first differs, ex- 

 ternally, in its more smooth, greenish, and somewhat radiated epi- 

 dermis ; the angular ridge running from the beaks backwards, pro- 

 duced l)y the strong compression of the hinge-margin ; and by a 

 contraction of the basal margin, near its posterior termination, so 

 as to form a sort of beak ; and internally hj the silvery, iridescent 

 nacre, and the slender, very oblique, cardinal teeth. U. radiatus has 

 the hinge very nearly the same as U. cotnplanatus ; 1 nit the nacre 

 is white, or somewhat livid, the shell never becomes so large, is 

 more regularly convex ; the epidermis is nearly smooth, shining, 

 and yellowish-green, with conspicuous rays of olive color. 



Unio nasutus. 



Fig. 71. 



Shell transversely oblong-lanceolate, hinge-margin compressed, anteriorly 

 rounded, posteriorly somewhat beaked ; epidermis dusky-green, obscurely rayed ; 

 cardinal teeth compressed, oblique ; nacre very bright, bluish- white, iridescent. 



Unio nasutus, Say, Nich. Encyc. (Anier. 1st ed.) iv. pi. 4, fiy. 1 (1816). — Conkad, 

 Unionidffi, 38, pi. 18, fig. l.— De Kay, Nat. Hist. New York, 191, pi. 20, fig. 2.39. 

 — Lea, Synops. .37. — Conrad, Synops. in Proc. Ac. Nat. Sc. vi. 252. 



Mya nasiita. Wood, Index, Snppl. pi. 1, fi<x. 4. 



Unio rosiratus, Valenc. Recueil d'Obs. de Zool., &c., par Humb. et Bonpl. ii. 233, pi. 53, 

 fig. 3. 



Eurynea nasuta, Stimpson, Shells of New England, 13. 



Lister, Conch, t. 151, fig. 6. 



Shell slender, oblong-lanceolate, very inequilateral ; beaks small, 

 pointed, and slightly elevated ; hinge-margin straight to more than 

 lialf the distance from the beaks to the posterior end, when it sud- 

 denly declines and continues straight to the point ; lower margin 

 nearly parallel with the upper, though somewhat rounded at the 

 middle, and towards the end turns rapidly upward towards the 

 point, which is considerably produced, so as to form a sort of snout. 

 An angular ridge passes backwards from the beaks to the tip, above 

 which the shell is very much compressed ; two or more radiating 

 furrows are usually seen traversing this portion. Surface rather 

 smooth, not much wrinkled by the lines of growth. Epidermis 



