AND DESCRIPTIONS OF NEW SPECIES, 93 



My Cabinet. 

 Cabinet of Professor Vanuxem. 

 Cabinet of H, C. Carey. 

 Cabinet of P. H. Nicklin. 

 Cabinet of the American Philosophical Society. 

 Cabinet of the Academy of Natural Sciences of Philadelphia. 

 Cabinet of the Lyceum of Natural History of New York. 

 Diam, 1-4, Length 1-7. Breadth 3-2 inches. 



Shell wedge-shaped, thick anteriorly and scaleniform ; substance of 

 the shell thick anteriorly and thin posteriorly ; beaks nearly terminal, 

 prominent and incurved, generally decorticated ; ligament rather 

 small ; epidermis yellowish brown, sometimes possessing oblique, in- 

 distinct, brown rays ; cardinal tooth short and slightly elevated, in the 

 left valve double and deeply cleft, in the right valve emerging from a 

 pit; lateral teeth thick and curving over the cardinal teeth; posterior 

 and anterior cicatrices both distinct; the smaller posterior cicatrix sit- 

 uated against the lateral tooth at its termination ; dorsal cicatrices sit- 

 uated on the under part of the cardinal tooth ; cavity of the beaks not 

 deep, rounded ; nacre thick and pearly anteriorly, thin and iridescent 

 posteriorly. 



Remarks. — This species resembles the scalenia of Rafinesque, but 

 more closely approaches the patulus (Nob.) and truncalus* (Swain- 

 son). It differs from the patulus in the rays being uninterrupted, and 

 in being much thicker. From the truncatus it differs greatly in the 

 cardinal tooth and in being wedge shaped and not cylindrical. 



* I will take advantage of this opportunity to correct an error, in stating in a former pa- 

 per that Lamarck and other European conchologists erroneously made the genus Unio femi- 

 nine. I sfiouid then have mentioned that Mr Swainson was an exception. 



Vol. IV.— Y 



