Maryland Geological Survey 559 



Occurrence. — Monmouth Formation. Brightseat, Brooks estate near 

 Seat Pleasant, and 1 mile west of Friendly, Prince George's County. 



Collections. — Maryand Geological Survey, New Jersey Geological 

 Survey. 



Outside Distribution. — Monmouth Formation. Navesink marl, New 

 Jersey. 



OSTREA FABA 11. Sp. 



Plate XXIV, Figs. 5, 6 



Description. — Shell an arcuate ellipse of moderate size and moderately 

 heavy. Eight valve feebly convex, lower (left) valve not known; umbones 

 flattened, inconspicuous; external surface roughened by irregular concen- 

 tric striations ; convex margin fluted by ten to twelve denticulate plica- 

 tions which are, however, confined to the border of the shell and abruptly 

 evanesce away from it; concave edge feebly and irregularly crenate; 

 ventral extremity evenly rounded ; not plicated ; hinge area obscure, liga- 

 ment area, very small, trigonal; muscle scar semi-elliptical, posterior in 

 position. 



Type Locality. — Brooks estate near Seat Pleasant, Prince George's 

 County. 



Dimensions. — Altitude, measured in straight line from tip of hinge line 

 to dorsal margin, 34.2 mm.; maximum latitude 12. 6 mm. 



The affinities of 0. faba n. sp. are doubtless with the 0. larva group, 

 but it is not referable to any of the described races. It is characterized by 

 the uniform width of the shell from the dorsal to the ventral margin, 

 suggesting with its slightly arcuate outline a large, flattened bean or a 

 bean pod. The radial sculpture is more restricted in its influence than in 

 any member of the 0. larva group, and the ventral margin more regular 

 in its outline. 



Occurrence. — Monmouth Formation. Brightseat and Brooks estate 

 near Seat Pleasant, Prince George's County. 



Collection. — Maryland Geological Survey. 



