MAKVLWI) (I i:0 LOGICAL Sl'ItVLY 199 



MATioN. Popes Creek, 2| miles above Popes Creek, Woodstock, Upper 

 Marlboro (deep cut near Chesapeake Beach E. R. station). 



CoUeclioiis. — Jolms Hopkins T^'niversity. ?ir.ii-v]aii(l Geological Survey. 



Family LEDIDAE. 



Genus LEDA Scluiiiuiclier. 



Leda improcera (Conrad). 



Plate LVI, Figs. 1, 2, 3, 4. 



Nucula improcera Conrad, 1848, Jour. Acad. Nat. 8ci. Phila., 2nd ser., voL i, p. 181, 



pi. -xiv, fi{?. 33. 

 Nucxilaii a improcera Conrad, 186.5, Amer. Jour. Conch., voL i, \k !"'• 

 Nuculana improcera Conrad, 1866, Smith. Misc. ColL (20^^), p. 3. 

 Leda improcera Clarlv, 1895, Johns Hopkins Univ. Circ, vol. xv, p. 5. 

 Leda improcera Clark, 1896, BiilL 141, U. S. Geol. Survcj', p. 8o, pi. xxviii, tisrs. 



la-Id (not le). 



Description. — '"'Elongate, very inequilateral, convex, polished, and 

 having fine indistinct concentric lines; anterior side produced, bicarin- 

 ated; the upper margin incurved toward the apex; extremity angulated." 

 Conrad, 1848. 



This species shows considerable variation in outline. Conrad's types 

 are of the more elongate form. If the more elevated form is a con- 

 stant variation it should be separated as a new variety or species. 



Length, 8 mm.; height, 4 mm. (typical). Length, 11 mm.; height, 7 

 mm. (elevated form). 



Occurrence. — Nanjemoy Formatiox. Popes Creek, Woodstock, 

 Head of Xanjemoy Creek, 2^ miles above Popes Creek. 



Collections. — Johns Hopkins University, Maryland Geological Survey. 



Leda parilis (Conrad). 

 Plate LYII, Figs. 1, 2, 2a. 



Nucula parilis Conrad, 1848, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. i, p. 132, 



pi. xiv, fig. 31. 

 Xucula parilis Clark, 1896, Bull. 141, U. S. Geol. Survey, p. 93. 



Description. — "Ovate, ventricose, with concentric lines; beaks medial; 

 anterior end pointed, angular; posterior end regularly rounded; an- 

 terior submargin carinated, hinge margin very oblique, straight from 



