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Mr. Barnes on the Genera Unio and Alasmodonta. 266 
carinate or depressed ; epidermis has generally a silky lustre; 
surface with smaller wrinkles placed between larger ones, 
or with transverse elevated distant furrows, or smooth; wy 
dinai teeth small, or not very large, sulcated or striated ; 
naker livid, cerulean, green, purple, red, violet, white, with 
various shades and mixtures of these colors; no cavity under 
the beaks. ; : ay 
Remarxs.~—The terms of the foregoing general description 
are taken from Mr. Say’s and from the six species of M. La- 
marck mentioned above. Thisis a very common shell, ofa reg- 
ular and uniform appearance, without prominence of parts, 
or sirongly marked characters; which perhaps induced M. 
Lamarck to say ‘it is nothing remarkable.”* Amidst a va- 
riety almost infinite, like that of the human countenance, 
there is still a characteristic identity of this species, which 
can scarcely be mistaken by an experienced observer. One 
variety of the Radiatus from the Saratoga Lake approaches 
nearest to this species, but the least appearance of rays for- 
bids its association. 
* * * Cardinal teeth small, direct. 
17. Unio Rapiatrus.—Shell broad-ovate, thin, fine- 
ly striated, glossy rayed, within bluish white, or 
tinged with red. 
Unio Ochraceous. Mr. Say. 
Mya Radiata. Mr. Dillwyn. 
Unio Radiata. M. Lamarck. 
American Conchology, plate 2, fig. 8. 
Tohabits lakes and rivers of North-America.  _ 
Cabinet of the Lyceum. My collection. 
Diam. ‘6—°9 Length 1:2—1:5 Breadth 2°0—2°5, 
Shell with the anterior side broad, thin and fragile, disks 
in old specimens somewhat convex ; in youug, depressed ; 
beaks slightly elevated and approximate; ligament eleva- 
ted; hinge margin elevated, compressed, carinate; basal 
margin commonly a little depressed, and sometimes areua- 
ted ; anterior margin narrow; posterior broad; anterior 
dorsal sub-truncate; epidermis greenish yellow or olive- 
town, rayed with dark green, and very finely striated trans 
*See An. Sans Vertebres, Vol. V1. p. 74, U. Georgina. 
Vou. VI.—No. oe 34 
