OF THE FAMILY OF NAIADES. 449 



pressed; valves thick ; posterior dorsal margin winged and connate ; a 

 large cardinal tooth in each valve; an irregular callous plane under the 

 ligament ; beaks compressed and scarcely projecting ; ligament conceal- 

 ed ; nacre white and iridescent. 



CFox River. Mr Schoolcraft. 

 Hab. < Wisconsan. Captain Douglass. 

 (^Ohio. W. Cooper. 



My Cabinet. 



Cabinet of Mr Barnes. 



Cabinet of Prof. Vanuxem. 



Cabinet of the New York Lyceum. 



Cabinet of Dr Mitchill. 



Cabinet of the Academy of Natural Sciences. 



Jllasmodonta complanata. Barnes. 



Diam. -9 — 1-4 inches. Length from beaks to base, 3 inches. 



Breadth 5 inches. 



Length from the top of the wing, 4*3 — 4-5 inches.* 



Shell triangular-ovate, inequilateral, transversely wrinkled, 

 compressed, the largest diameter being nearly 2-3ds of the dis- 

 tance from the beaks to the base ; substance of the shell thick ; 

 valves elevated into a moderately sized wing over the ligament, 

 and connate; this wing is traversed at right angles to the 

 wrinkles, by obscure undulations reaching to the beaks ; beaks 

 much compressed and scarcely projecting, crowned by seve- 

 ral double concentric undulations, which terminate in a point ; 

 ligament concealed in the wing ; sinus subquadrate ; epider- 

 mis dark brown and irregularly wrinkled; cardinal tooth 

 thick, elevated, sulcated, and diverging from the beaks ; a wide, 

 irregular callous plane extends under the ligament ; cicatrices 

 in the anterior margin three, and irregular ; in the posterior 

 margin two, confluent and scarcely perceptible ; dorsal cica- 

 trices very perceptible ; cavity of the beaks and disk small ; 

 nacre white and iridescent. 



Remarks. — This shell, first described by Barnes, is a rare 



* See Barnes's description ; my specimen is rather more ventricose. 



