196 SYSTEMATIC PALEONTOLOGY 



over a wedge-shaped tooth in the right valve; a longer posterior lateral 

 tooth in the left valve received between two subequal less-prominent lami- 

 nae in the right valve; teeth crenulated on their opposite surfaces; carti- 

 lage pit persistent; internal border of the valves smooth or faintly radially 

 striated; adductor scars distinct; pallial line distinct; pallial sinus small. 



This species is a shallow, particularly brackish-water form and fre- 

 quently occurs in great numbers, almost to the exclusion of all the other 

 mollusca. It is a distinctly southern warm-water form and has never 

 been found north of Maryland. 



The earliest occurrence of this species is in the Pliocene of the Caro- 

 linas and Florida. In the Pleistocene it ranges from Maryland south- 

 ward to Florida and thence along the Gulf Coast to Mexico and in the 

 Recent from Alabama to Vera Cruz, Mexico. 



Width, 50 mm.; height, 4G mm.; thickness. 33 mm. 



Occurrence. — Talbot Formation. Wailes Bluff near Cornfield Har- 

 bor and Potomac shore between Float and Poplar Hill Creeks, St. Mary's 

 County; east side of aSTaniemoy Creek, Charles County; near Middle 

 Eiver, Baltimore, Sparrows Point well, Baltimore County. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 and U. S. National Museum. 



Superfamily SOLENACEA. 

 Family SOLEN1DAE. 



Genus ENSIS Schumacher. 



Ensis directus (Conrad). 



Plate LV, Figs. 9, 10. 



Solen directus Conrad, 1843, Proc. Acad. Nat. Sci. Phila., vol. i, p. 325. 

 Ensis americana Dall, 1889, Bull. U. S. Nat. Mus., No. 37, p. 72, pi. 53, fig. 4; 



pi. lv, figs. 4, 5. 

 Ensis directus Dall, 1900, Trans. Wagner Free Inst. Sci., vol. iii, pt. v, pp. 



954, 955. 

 Ensis directus Glenn, 1904, Md. Geol. Survey, Miocene, p. 291, pi. lxxi. 



figs. 2, 3. 



