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SPECIES XL. Obliquaria obliquata (Unio 

 obliquata.) 



Shell very thick, ventricose ; triangularly oval ; 

 the three sides arcuated ; a slight oblique longi- 

 tudinal depression; epidermis almost smooth, 

 black ; nacre purple rose colour. Length -^ 

 diam. T 6 7 axis ^ of the breadth. 



A pretty species ; having a fine purple nacre 

 with iridescent changes ; found in the Kentucky 

 river ; breadth two to three inches ; lamellar tooth 

 long, carinated ; fossule large, distinct ; cardinal 

 tooth wrinkled ; muscular impressions deep ; 

 apices prominent, truncated. 



SPECIES XLI. Obliquaria triangularis (Unio 

 triangularis.} 



Shell very thick, ventricose, triangular ; poste- 

 rior face straight ; apices prominent ; no longi- 

 tudinal depression ; epidermis brown, almost 

 smooth ; nacre roseate white. Length diam. 

 axis | of the breadth. 



Var. 1 . nigrescens epidermis blackish : 

 nacre white. 



Common in the Ohio ; breadth sometimes four 

 inches ; cardinal tooth [very large, furrowed ; 



