31 



Amhkican East Coast Arcas 31 



cardinal area elevated, anterior square or slightly raised; teeth fine and vertical at the 

 center, rapidly becoming oblique and longer distally; sides of the teeth grooved; anterior 

 margin of the shell rounded with an angle at the hinge-line, basal margin nearly parallel 

 to the hinge, posterior margin in young shells nearly straight and perpendicular to the 

 hinge and base lines, in larger specimens somewhat produced below and emarginate 

 above with a sharp angle at the hinge-line; inner margin with fine crenulations. 



This species lies between Barbalia and Scapharca. The outline of the shell and 

 form of the cardinal area are like the Scapharcas, but the teeth and the close grooving of 

 the cardinal area are like Barbatia. The ribbing is intermediate between the two groups. 



Dimensions. — Lon. +12. 5,-24; alt.-f-2.5,-i7; semidiam. 8.5 mm. 



Occurrence. — Lisbon, Alabama, the Eocene of Orangeburg, South Carolina, and ac- 

 cording to Haldeman from the Eocene of Virginia. — Dall. Claiborne Eocene of Clai- 

 borne, Alabama. — C. U. Museum. 



Area Vaughani Casey 

 Plate VII, Figure 1 1 



Area rliomhoidella var. Vaughan, U. S. Geol. Surv. , Bull. 142, pi. 3, fig. 8. 1896. 

 Area vaughani Casey, Acad. Nat. Soi. Phila,, Proc. for 1903, p. 265, 1903. 



" * * * A species, quite common in the Lower Claiborne at St. Maurice, La., and 

 allied somewhat to rhomboidella Lea. It attained a length of more than 20 mm., with 

 a height of 12 mm. or more, obliquely rhomboidal, moderately inequilateral, rounded an- 

 teriorly and posteriorly and broadly rounded ventrally. It is moderatelj' inflated, the 

 radiating concavity at the middle of the umbones almost obsolete and having merely 

 slightly wider intervals between the ribs, the latter 41-43 in nimiber. The hinge-line is 

 long and straight, the teeth becoming larger and very oblique laterally but well devel- 

 oped throughout, with their sides finely ribbed, giving to each tooth a bipectinate ap- 

 pearance. The area under the beaks is ample and broadly, divaricately striate. This 

 species differs from rhomboidella in its much larger size, more numerous ribs, rounded 

 ventral edge and many other characters, and may be named vaughani. A fair illustra- 

 tion of it was given by Mr. Vaughan (Bull. Geol. Surv., 142, PI. Ill, fig. 8), in whose 

 honor it is named. A modification of the true rhomboidella, but still smaller in size, also 

 occurs sparingly at St. Maurice." — Casey, 1903. 



Unless A. Vaughani grows to a larger size than that given in the description the 

 statement of the comparative size of Vaughani and rhomboidella would not hold true. 

 The type of rhomboidella was a young specimen. Unlike rhomboidella, in .4. Vaughatii 

 the ribs are only slightly or not at all grooved. 



Dimensions. — Lon.+7,-i3; alt.-|-2,-i2; semidiam. 5 mm. 



Occurrence. — Lower Claiborne of St. Maurice, Louisiana. — C. U. Museum. 



Area invidiosa Casey 



Area invidiosa Casey, Acad. Nat. Sci. Phila., Proc. for 1903, p. 264, 1903. 



"From the Red Bluff formation of Mississippi I have before me specimens of a small 



