92 OBSERVATIONS ON NAIADES, 



Shell striate, transverse, inequilateral; valves thin; beaks slightly prominent ; um- 

 bones rugose; cardinal tooth oblique, lamelliform, single in the left valve and dou- 

 ble in the right; lateral tooth long and nearly straight; nacre bluish white. 



Hab. Brazil, Mrs Mawe. 



My Cabinet. 

 Diam. •?, Length 1, Breadth 1*9 inches. 



Shell subrectangular, transverse, slightly compressed and rounded 

 nearly alike at both ends ; substance of the shell rather thin ; beaks 

 slightly prominent, surrounded by wrinkles forming acute angles vv^ith 

 each other, extending over the umbones and some distance down the 

 umbonial slope; ligament linear; epidermis dark brown and wrinkled ; 

 cardinal tooth oblique, lamelliform, single in the left valve and double 

 in the right ; lateral teeth long, lamelliform and nearly straight ; anterior 

 and posterior cicatrices both confluent ; dorsal cicatrices in the centre of 

 the cavity of the beaks ; cavity of the beaks wide and shallow ; nacre 

 bluish white and slightly iridescent in posterior margin. 



Remarlis. — The specimen from which the above description was made 

 was sent to me by Mrs Mawe of London. This species approaches 

 in outline to some of the varieties of the U. complanatus (Solan.). In 

 the flexuous rugosities of the beaks it resembles the U. corrugatus 

 (Lam.) and U. cxruleus (Nob,). It diflers however from them both 

 in outline. 



Unio Decisus. Plate XII. fig. 23. 



Testa inaqiiilaterali, ohliqua,cuneata, scalend, crassdque; valvulis percrassis; na- 

 tibus elevatis, incurvatis,fcre terminalibus; dentibus cardinalibus aliquantulum par- 

 vis, lateralibus crassis; margarita alba. 



Shell inequilateral, oblique, wedge shaped, scaleniform and thick; valves very 

 thick; beaks elevated, incurved, nearly terminal ; cardinal teeth rather small; lateral 

 teeth thick ; nacre pearly white. 



Hab. Alabama river. Judge Tait. 



