OF THE FAMIl.\ OF NAIADES Id 



10. I'm.) Ibis. Plat.' XI. fig. 18. 



Testi\ anguato-ettiptici, inoquUaterali, srib-ventricoaa; vahulu temri- 

 bus; natibtus prominulis ; dente cardinali in oalvuld riniatrd, duplici, in 

 dextin aub-bifido, parvo, erecto; dmtibua later alibtulongu tenutbuaqtu ; 

 margarita sub-ccervleo-albd. 



Shell narrow-elliptical, inequilateral, slightly ventricoso : valv< - thin, 

 beaks slightly prominent 5 cardinal teeth doable in 1 1 » « - left valve, sub- 

 bifid in the right, Miiall, erect; lateral teeth long ami thin; nacre bluish 

 white. 



Hab. Ohio. T. G. Lea. 



My Cabinet 



Cabinet of T. G. Lea. 



Cabinet of Prof. Vanuxem. 



Diam. -5, Length -8, Breadth 1*6 inches. 



Shell long-elliptical, inequilateral, slightly ventricose; sub- 

 stance of the shell thin, showing the rays through it. rather 

 more dense before than behind: beaks slightly prominent, 

 approaching, crowned with double concentric undulations 

 when they are not decorticated: ligament rather long and 

 thin: epidermis yellowish green, transversely wrinkled, mark- 

 ed with many oblique diverging rays passing from the beaks to 

 the margin; cardinal teeth double in botli valves, small, erect, 

 and sharp; lateral teeth long, bladed, slightly curved and situ- 

 ated on the edge of the margin in contact with the ligament; 

 anterior cicatrices distind : posterior cicatrice, confluent and 

 scarcely perceptible; dorsal cicatrices within the cavity of the 

 beaks, the largest on the under pari of the callus; nacre verj 

 thin, milk while anteriorly, bluish white and iridescent pos- 

 teriorly. 



Remarks. — This species most resembles the calceoku. It 



differs, however, entirely in the teeth, which are distinct and 

 well defined. The calceoku approaches closely to the uvnus 

 jfflasmodonta of Say. This j> ], gg ventricose and possesses 

 more rays. 



vol. in. — 5 T 



