UNIO SUBTENTUS. 



SPECIFIC CHARACTER. 



Transverse; anterior dorsal margin sculptured with 

 small elevated costae. 



SYNONYM. 



Unio SUBTENTUS. Nobis. Jour, Acad. Nat. Sc. vol. v. 

 p. 130. 



DESCRIPTION. 



Shell transversely oblong-suboval, very widely and slight- 

 ly contracted at base ; brownish olivaceous, obsoletely ra- 

 diated : posterior side short regularly rounded : cavity of 

 the hinge membranes^ behind the summits elongate, some- 

 what fusiform, acute : summits hardly elevated, decorti- 

 cated : anterior basal angle a little prominent, rounded : 

 anterior dorsal and anterior margins^ from the umbo to 

 the angle with numerous, subramous, slightly arquated, 

 oblique, parallel costae : within reddish fulvous : cavity of 

 the umbo not deep : primary teeth somewhat longitudinal : 

 lateral teeth slightly arquated, hardly reaching the extre- 

 mity of the sinus of the cartilage : pallcal impression ex- 

 tending anteriorly a little beyond the muscular impres- 

 sion : smaller posterior muscular impression oblong, of 

 moderate size. 



PLATE XV. 



