44 BuivLETiN 5 314 



138 FOSSIL SHELLS. 



margin perfectl}^ rectilinear, angulated at the ex- 

 tremities, the anterior one a little projecting : teeth 

 in a continued, uninterrupted line, parallel, except- 

 ing at the two extremities of the line, which de- 

 cline a little, and the teeth are there decidedly 

 longer and oblique with respect to the others of 

 the range : posterior end obliquely rounded to the 

 base : base nearly rectilinear and parallel to the 

 hinge margin, and deeply crenated on the inner 

 margin : anterior end produced below the middle, 

 and rounded, and a little contracted near the supe- 

 rior angle. 



Length from the hinge margin to the base one 

 inch and three-tenths, breadth two inches and a 

 half. 



This resembles a species found recent and ver}^ 

 common in the West Indies, and which I have not 

 ascertained to be distinctly described. That shell, 

 however, is proportionally longer, the anterior ex- 

 tremity only of the line of teeth declines a little, 

 and the series is slightly dislocated a little before 

 the apices of the shell. 



2. A. centenaria. PI. x. fig. 2. Shell transversely- 

 oval, subrhomboidal, obtusely contracted at base, 

 with numerous alternate longitudinal striae. 



Description. Striae from one hundred to one 

 hundred and eighty and more in number : disap- 

 pearing on the hinge margin ; with hardly obvious 

 transverse minute wrinkles, and larger, remote, 

 irregular ones of increment : beaks but little pro- 



[J. A. N. S., Phila., ist Ser., VoL IV, 1824.] 



