19 



American East Coast Arcas 19 



Tuomey's shell was proportionately longer than Conrad's. 



Occurrence. — Miocene of Virginia, on the James River below City Point, Petersburg, 

 and on the Ware River, Gloucester County; Darlington, vSouth Carolina; Sumter Dis- 

 trict, South Carolina. — Da 11. 



Area virginiae Wagner 



Plate IV, Figures 2, 3, 4 



Area Virginia W. AVagner, Trans. Wagner lust., v., pi. i, fig. 3 (fide Dall). 

 Area Virginia Bronn, Index Pal. Nomencl., p. 99, 1848; Syst., p. 281, 1849. 

 Barbalia (Granoarca) Virginia Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt, 4, p. 627, pi. 32, 



fig- 23. 1898. 

 Area (Barbatia) Virginia Glenn, Maryland Geol. Surv., Miocene, p. 392, pi. 106, fig. 8, 1904. 



''Area virginies is a large, solid, elongated shell, equivalve but very inequilateral, 

 the beaks being situated near the anterior fifth of the length, low and prosogyrate, dis- 

 tant, and separated by a wide cardinal area with numerous (nine) slightly angular longi- 

 tudinal concentric grooves; sculpture of about twenty-five strong radial ribs, smaller on 

 the posterior dorsal area, somewhat flattened, and on the posterior part with a shallow, 

 wide mesial furrow; hinge-line .65 as long as the shell; teeth vertical, in two series, be- 

 ginning mesially very small, distally larger, and with a tendency to break up or become 

 irregular; muscular impressions deep; margin fluted in harmony with the ends of the 

 ribs. Lon. 83, alt. 52, diam. 42 mm. 



"This shell is about midway in its characters between Barbatia {Granoarca), Ana- 

 dara, and Scapharea, illustrating very well the manner in which the subordinate groups 

 of the genus /4rra intergrade * * *." — Dall. 



Occurrence. — Miocene of Virginia, (Nansemond River?) — Dall. St. Mary's Miocene 

 of St. Mary's River, Maryland, (imperfect, probably this species). — Glenn. Miocene of 

 Claremont Wharf, James River, Virginia. — C. U. Museum. 



Area centenaria Say 



Plate IV, Figures 5, 6, 7 



Area centenaria Say, Acad. Nat. Sci. Phila., Journ., ist. .ser., vol. 4. p. 138, pi. 10, fig. 2, 1824. 

 Striarca (Area centenaria Conrad, Acad. Nat. Sci. Phila., Proc. for 1S62, pp. 290, 580, 1863. 

 Barbatia (Striarca) centenaria Dall, Wagner Free In,st. Pci., Trans., vol. 3, pt. 4, pp. 615, 62S, 



1898; pt. 6, p. i6or, 1903. 

 Area (Barbatia) centenaria Glenn, Maryland Geol. Snrv., Miocene, p. 391, pi. 106, figs. 5, 6, 1904. 



"Shell transversely oval, subrhomboidal, obtusely contracted at the base with nu- 

 merous alternate longitudinal striae. 



"* * * Striae from one hundred to one hundred and eighty and more in ntunber: 

 disappearing on the hinge margin; with hardly obvious transverse minute wrinkles, and 

 larger, remote, irregular ones of increment: beaks but little prominent, not remote: base 

 widely but not deeply contracted, nearly parallel with the hinge margin: anterior and 

 posterior margins obtusely rounded: series of teeth rectilinear, uninterrupted, decurved 

 at the tips; space between the beaks with numerous grooves proceeding from the teeth: 



