44 Palaeontographica Americana 44 



Occurrence. — Upper bed (Miocene) at Gaskin's Wharf, on the Nansemond River, 

 sixteen miles below Suffolk, Virginia. — Dall. Miocene of North Carolina. — C. U. 

 Museum. 



Area arata Say 



Plate X, Figures 6, 7, 8 



Area arata Say, Acad. Nat. Sci. Phila., Journ., 1st. ser., vol. 4, p. 137, pi. 10, fig. i. 1S24. 



Area arata Conrad, Fos. Med. Tert., p. 58, pi. 30, fig. 6, 1845. 



Seapharca (Area) arata Conrad, Acad. Nat. Sci. Phila., Proc. for 1S62, p. 579, 1S63. 



Scapharca {Scapharea) arata Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, pp. 643, 644, 645, 



1898. 

 Area arata Bullen Newton, Geol. Mag., u. s., vol. 9, pp. 304, 305, 1902. 

 Area (Scap/iarca) arata Glenn, Maryland Geol. Surv., Miocene, p. 38S, pi. 105, figs. 7a, 7b, 1904. 



"Shell transversely oblong, subrhomboidal, with about twenty-six longitudinal ribs; 

 basal edge nearly parallel to the hinge margin, which latter terminates anteriorly in an 



angle. 



"Ribs somewhat flattened, as wide or rather wider than the intervening spaces; the 

 whole surface concentrically wrinkled: umbones not remarkably prominent: apices re- 

 mote, the intervening space rhomboidal, with continued indented lines, arcuated under 

 the apices: hinge margin perfectly rectilinear, angulated at the extremities, the anterior 

 one a little projecting: teeth in a continued, uninterrupted line, parallel, excepting at the 

 two extremities of the line, which decline a little, and the teeth are there decidedly longer 

 and oblique with respect to the others of the range: /oj/fw;- fwrt' obhquely rounded to 

 the base: base nearly rectilinear and parallel to the hinge margin, and deeph^ crenated on 

 the inner margin: atiterior eiid produced below the middle and rounded, and a little con- 

 tracted near the superior angle. 



"Length from the hinge margin to the base one inch and three-tenths, breadth two 

 inches and a half * * "^.''—Say, 1824. 



In the original description anterior and posterior and length and breadth are inter- 

 changed. 



Dimensions. — Small valve. Ion. +12,-23; alt. +3, -18; semidiam. 9 mm. 



Occurrence. — Miocene of St. Mary's County, Maryland. — Dall. St. Mary's fonna- 

 tion, St. Mary's River (quite rare). — Glenn. St. Mary's, Maryland. — C. U. Museum. 



Area improcera Conrad 

 Plate X, Figures 9, 10, 11, 12, 13, 14, 15, 16 



Area improcera Conrad, Fos. Med. Tert., p. 60, pi. 31, fig. 5, 1845. 



Seapharca (Area) improcera Conrad, Acad. Nat. Sci., Phila., Proc. for 1862, p. 579, 1S63. 



Area plieatura (juvenis) Heilprin, Acad. Nat. Sci., Phila., Proc. for 1881, p. 451, 1882. 



Seapharca (Scapharea) improcera Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, pp. 643, 644, 



646, 1898. 

 "Trapezoidal; disk slightly flattened from beak to base; ribs about 34, square, ap- 

 proximate, little prominent, convex and crenulated anteriorly; anterior margin rounded, 



