26 Paleaontographica Americana 26 



and extending backward to a point about half way from the beaks to the posterior ex- 

 tremity of the hinge in the adult, shorter in the 3'^oung; ligament area with transverse 

 grooves which are stronger in front of the beaks ; posterior part of the cardinal area longi- 

 tudinally striated; hinge-line as long or nearly as long as the shell; umbonal ridge angu- 

 lar; shell long and rectangular, anterior margin rounded, ventral nearly straight and de- 

 scending so that the lowest point of the shell is at the posterior end, posterior end usually 

 emarginate and nearly at right angles to the hinge; hinge narrow; line of teeth straight, 

 posterior teeth oblique, anterior teeth vertical except at the end of the hinge, where a few 

 are usually bent at a right angle, as in ^. ponderosa. 



It is apparent that Conrad's Noetia protexta from the Miocene of North Carolina is 

 the same as Say's A. incile. The specimen of A. trigintinaria Conrad (Acad. Nat. Sci. 

 Phila., Proc, p. 289, 1862), in the museum of the Academy, is intermediate between 

 incile and limida. It is not a separate species, but rather a variety of incile. It is from 

 the Miocene of South Carolina. A. iticilis Kerr, Geol. Rep. N. Car., 1875, is a misprint 

 for A. incile. 



Dimensions. — Lon. +8,-26; alt. +5, -18; diam. 22 mm. Large valve. — L,on. 45, alt. 

 30, semidiam. 14 mm. 



Ocairrcnce. — Miocene of Maryland, Virginia, and North Carolina; near Darlington, 

 South Carolina, at various points near and at the Natural Well, Duplin County, North 

 Carolina; Petersburg, Dinwiddie, York River, and borders of the Dismal Swamp, Vir- 

 ginia, and Choptank, Maryland. — Dall. Miocene of Grove 'WTiarf, Evergreen, Kingsmill, 

 Yorktown, Bellefield and Shackleford, Virginia; Magnolia, North Carolina; Dariington 

 C. H., South Carohna; Tertiary of James River, Virginia. — C. U. Museian. 



Area lirtiula Conrad 

 Plate V, Figure 26; Plate VI, Figures i, 2, 3, 4, 5 



Area liniula Conrad, Fos. Tert. Form., p. 15, pi. i, fig. i, 1832; Fos. Med. Tert., p. 60, pi. 31, fig. 



3. 1845. 

 Noetia (Area) limula Conrad, Acad. Nat. Sci Phila., Proc. for 1862, p. 580, 1863. 

 Area {Noetia) limula Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, pp. 617, 631, 659, pi. 31, 



figs. 14, 14b, 1898. 



"Oblong, sinuous, rather thin; ribs mmaerous, crossed by striae, which are equally 

 distinct in the interstices; ribs double on the posterior side where they alternate with 

 fine lines; irmbo angulated behind; hinge area narrow, oblique, and transversely striated ; 

 basal margin contracted near the middle; inner margin crenate * * *. 



"This shell has a general resemblance to Area ponderosa, of Say, but cannot be con- 

 founded with that species." — Conrad, 1832. 



Dall (Wagner Free Inst. Sci., Trans., vol. 3, p. 632, 1898) gives the two following 

 varieties of A. limula: 



Area limula var. platyura Dall 



Pliocene of the Caloosahatchie and Alligator Creek * * *. 



