292 SYSTEMATIC PALEONTOLOGY 



Ensis ensiformis Conrad. 

 Plate LXXI, Figs. 4, 5, 6. 



Solen ensiformis Conrad, 1843, Proc. Acad. Nat. Sci. Phila., vol. i, p. 326. 

 Solen ensiformis Conrad, 1845, Fossils of the Medial Tertiai-y, p. 76, pi. xliii, lig-. 8. 

 Unsis ensiformis Conrad, 1863, Proc. Acad. Nat. Sci. Pliila., vol. xiv, p. 571. 

 Ensis ensiformis Meelv, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 12. 

 Ensis ensiformis Dall, 1900, Trans. Wagner Free lust. Sci., vol. iii, pt. v, p. 955. 



Description. — " Linear, slightly curved, gradually narrowed from the 

 middle to the posterior extremity, which is subcuneiform ; anterior mar- 

 gin obliquely subtruncated." Conrad, 1845. 



Shell thin, fragile ; teeth two in left valve, separated by a very narrow 

 deep cleft, in right valve one; anterior extremity flaring; posterior ex- 

 tremity tapered, rounded and gaping. 



Although quite abundant at Cove Point, it is almost impossible to 

 obtain it except in fragments. 



Occurrence. — St. Mary's Formation. Cove Point, St. Mary's Eiver. 

 Ghoptank Formation. Jones Wharf, Sand Hill, Greensboro. Calvert 

 Formation. Fairhaven, Plum Point, Eeed's. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Superfamily TELLINACEA. 

 Family PSAMMOBIID/E. 



Genus PSAMMOBIA Lamarck. 



Subgenus PSAMMOBIA s. s. Dall. 



PSAMMOBIA GUBERNATORIA U. sp. 



Plate LXXI, Figs. 7a, 7b. 



Description. — Shell long-ovate, thin, fragile, depressed or flat, inequi- 

 lateral; anterior end being broader and longer than the posterior one; 

 beak very low; anterior side slightly curved and for some distance from 

 the beak nearly parallel with the base; anterior end regularly rounded 

 and broad; posterior side with broad projecting hinge plate; posterior 

 side declining; posterior end rounded and more nearly on line of base 

 than anterior end; base only slightly curved; lateral teeth none, cardinals 

 in right valve two; posterior adductor scar oval, anterior one larger and 



