38 



lamellar tooth short ; no fossule ; cardinal tooth 

 somewhat wrinkled ; ligament horizontal.* 



Third Sub-genus QUADRULA. 



Form square, but anteriorly rounded, slightly 

 transversal . 



SPECIES XXVIII. Obliquaria flava ( Unio 

 flava.) 



Shell somewhat thick, convex, and sloping 

 posteriorly ; apices slightly prominent, entire, ru- 

 gose ; epidermis nearly smooth, yellowish brown ; 

 nacre flesh coloured. Length ^ diam. f axis 

 f of the breadth. 



A fine species, found only in the small rivers 

 falling into the Kentucky, Salt, or Green rivers. 



* The Unio nasutus of SAY, ought to belong to this 

 sub-genus; and the following species, which I observed in 

 the river Hudson, resembles it much : may not this be a 

 variety ? 



Obliquaria attenuata, elliptical, dilated, attenuated^ 

 with a posterior slope; ligament horizontal; epidermis 

 rugose, dark brown ; nacre pale rose colour. Length 1-2 

 diam. 1-4 axis 1-4 of the breadth. Breadtli four 

 inches. 



