^6 Palaeontographica Americana 36 



Anterior and posterior are reversed in the original description. 



Ribs thirty-eight to forty-three, usually as wide or wider than the interspaces, some- 

 what more closely set on the middle of the valve ; ribs near the umbonal ridge and gen- 

 erally on other parts of the shell with a finer secondary groove each side of the main 

 longitudinal groove ; ribs beaded ; cardinal area rather narrow with about three or four 

 irregular, concentric grooves and a transverse line between the beaks, cardinal area 

 wider in front with raised margin posteriorly and near the beaks anteriorly; beaks mes- 

 ially sulcate; posterior margin straight in the adult, emarginate in the young; basal 

 margin slightly curved to arcuate, sometimes sinuate. 



With age A. lienosa becomes long, narrow and inflated with produced posterior end 

 and sometimes a sinuate basal margin and the cardinal area is wider with irregular grooves. 

 A. protrada Rogers, from Prince George County, Virginia, is probably an old A. lietiosa. 

 A specimen from Kingsmill, Virginia, shows small, even teeth pointing awa}' from the 

 beaks, as in Rogers' specimen, though they are somewhat longer at the ends of the hinge 

 and as a rule the teeth in old A . /ienosa are larger and less regular. The teeth of />ro- 

 trada resemble those of A. sedicostata. The lines of growth near the beak as drawn in 

 Ro<^ers' figure do not show the alation of the young A. lienosa. The \^irginia specimens 

 resembling A. protrada show this alation. Shells from North Carolina approach protrada. 

 Heilprin united lienosa B,nAflorida?iaT=secticostata. One of his specimens from the Cal- 

 oosahatchie was six inches long and three inches high. A. hypomela lacks the posterior 

 emargination or alation of A. lienosa. 



Dimensions. — Lon. + 18,-40; alt. +6,-30; semidiam. 17 mm. Lon. of a large valve 



87, alt. 51 mm. 



Occurrence. — Miocene of York and James River, Virginia, of Wilmington and Duplin 

 County, North Carolina, and of the upper bed at Alum Bluff, Florida; Pliocene of the 

 Waccamaw District, South Carolina, the Caloosahatchie River, Alligator and Shell 

 Creeks, Florida * * *. Not known in the recent state. — Dall. Miocene of Kingsmill, 

 and Bellefield, Virginia; Duplin County, North Carolina; the upper bed at Alum Bluff, 

 Florida. — C. U. Museum. 



Area secticostata Reeve 

 Plate VIII, Figures 3, 4, S 



Area secticostata Reeve, Conch. Icon., Area no. 38, pi. 6, 1S44. 

 Anadara secticostata Gray, Ann. Nat. Hist., 2d. ser., vol. 19, p. 371, 1857. 

 Anomatocardia Ftoridana Conrad, Am. Journ. Conch., vol. 5, p. 108, pi. 13, fig. 2, 1869. 

 Scapharca secticostata Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, pp. 636. 637, 659, 1898; 

 pt. 6, p. 1616, 1903. 



"Area testa elongato-ovatd, gibbosissitna, tenuiculA, lateribus superne angulalis, infrci 

 subobligiu; roiiindatis; albidd, fuscescente pariim tinetd; radiatim costatd, costis 7itimerosis, 

 angustis, ad quadragenas, quatnplurimis suleo subprnfondo divisis; ligamenti are& elongatd, 

 latiusculd; umbonibus tumidis. 



"The Cut-Ribbed Ark. Shell elongately ovate, very gibbous, rather thin, sides an- 

 gtilated at the upper part, rather obliquely rounded beneath; whitish, partially stained 



