Telling spaces, excepting on the anterior side, where they are 

 broader, and simply wrinkled, those of the anterior part of 

 the disk have one or two longitudinal impressed lines; they 

 are crossed by numerous transverse, elevated lines, which 

 are hardly more distant from each other than their own 

 width ; intervening spaces wrinkled : beaks distant, curved 

 a little backward, and the tip a little behind the middle of 

 the hinge margin : area flattened, a little curved, rather spa- 

 cious, with obvious impressed, oblique lines: hinge margin 

 rectilinear, with small, numerous teeth : posleiior margin 

 regularly arquated : base subrectilinear, very deeply cre- 

 nated : anterior margin oblique, rectilinear : anterior side 

 abruptly compressed. 



OBSERVATIONS. 



This is a fossil shell. I am indebted for a specimen to 

 my excellent correspondent, the late Stephen Elliott, of 

 Charleston, who informed me that he obtained it from 

 the Santee river, below the confluence of the Consraree 

 and Wateree rivers. 



It seems to be related to some of the varieties of A. gra- 

 nosa, L. ; but the ribs are more slender ; the apex is curv- 

 ed a little backward, &c. 



REFERENCE TO THE PLATE. 



Fig. 2, Exterior and Interior views. 

 PI. 36. 



