2 7 Amekican East Coast Akcas 



Shell with the posterior end of the cardinal border elevated and forming nearly a 

 right angle wdth the posterior margin of the valves, thus giving the posterior part of the 

 shell a higher and more angular look, which at first seems very distinct. 



Area timula var. filosa Conrad 



Noetia ponderosa Say, var. A^. carolinensis Conrad, Proc. Acad. Nat. Sci. rhila.,for 1862, p. 290; 



not Area carolinensis Wagner, 1847. 

 Area earolifiensis Heilprin, Proc. Acad. Nat. Sci. Phila. for 1881, p. 450. 

 Noetia filosa Conrad, Kerr's Geol. Rep. N. Car., App. A, p. 20, pi. 4, fig. 3, 1875. 



Miocene of North Carolina : at Sullivan's marl-pit, Green County, North Carolina, 

 eight miles east of Snow Hill * * *. 



This variety has more ntmierous (thirty-five) ribs when adult and a less angular 

 outline than the typical form. 



* * * A variety analogous to platyura is possessed by all the species of Noetia, but 

 is perhaps more conspicuous in A . limula * * '^. 



In A. limula there are from twenty-eight to thirty-five ribs. In the long, rounded 

 form they are often narrower and more crowded anteriorly, as in A. incile. Ribs about 

 the umbonal ridge often with a fine riblet Uke the interstitial rib in the mesial sulcus; in- 

 terspaces crossed by even, concentric lines which give a beaded appearance to the inter- 

 stitial ribs but are less marked on the primary ribs as a rule ; posterior strip of the car- 

 dinal area not covered by the ligament ; ligament transversely grooved, grooves stronger 

 in front; anterior margin of the cardinal area elevated, posterior rounded; teeth as in .4. 

 potiderosa; muscle scars with raised margins; anterior margin of the shell rounded, basal 

 curved or sinuous with the lowest part of the shell usually near the posterior end; pos- 

 terior margin usually with a bend near the hinge. 



Typical yi. /zw?</a has a sinuous base and an angle near the top of the posterior 

 margin. It is separated from A. incile by its larger size, irregular outline, by the angle 

 in the posterior margin and especially by the hinge and position of the beaks. The long, 

 irregular shape and more anterior beaks separate it from A. ponderosa. Specimens from 

 South Carolina, probably from the Pliocene, are, however, closely related to A. ponderosa. 

 They have a more rectangular outline than typical limula, a relativelj' longer hinge-line, 

 less anterior beaks, and have little or no bend in the posterior margin. A. limulus Mor- 

 ton 1834 and A. limatula Emmons, 1858, are misprints for A. limula. Conrad (Acad. 

 Nat. Sci. Phila., Proc. for 1864, p. 211) withdrew his variety f(i/'(;//«<?/;jv'.f from the spe- 

 cies ponderosa. 



Dimensions. — Lon.+22,-35; alt. -f 9, -36; semidiam. 19 mm. 



Occurrence.— '\i\ocene: North Carolina, at Wilmington, New Berne; Virginia, at 

 various points on the York and James Rivers; also in Mar>-land and South Carolina, and 

 at Heislerville, Ctmiberland County, New Jersey. Pliocene: De Leon Springs, Florida; 

 in the marls of the Caloosahatchie and Shell Creek; near Brunswick, Georgia; Wacca- 

 maw beds. South Carolina. — Dall. Pliocene of Waccamaw, South Carolina, and the 

 Croatan beds, North Carolina. — C. U. Museum. 



