710 SYSTEMATIC PALEONTOLOGY 



double, the dorsal plate probably discrete in the young but larger and fused 

 with the dorsal margin in the adults; left cardinal A -shaped, placed 

 directly in front of the chondrophore ; lateral laminae prominent, the 

 anterior shorter and more elevated than the posterior, both of them flat- 

 tened upon their summits and striated transversely ; adductor muscle scars 

 obscure, the anterior broadly lenticular and falling below the median hori- 

 zontal, the posterior larger and rudely quadrilateral ; pallial line very near 

 the base; sinus short, uniform in width throughout its extent, obliquely 

 ascending and rounded at its extremity, not attaining the median vertical. 



Dimensions. Altitude 3L5 mm., latitude 3? mm., semi-diameter, 

 11.5 mm. 



Type Locality. Brightseat, Prince George's County. 



This species is well characterized by its high trigonal outline and 

 obtusely angulated anterior and posterior carinae. The species was at first 

 mistaken for C. appressa Gabb from Pataula Creek, Georgia, but it is 

 readily separable, whenever interiors can be obtained, by the transversely 

 striated laterals. It is named for Stanley Worden, who has so greatly 

 assisted in the study of the Upper Cretaceous mollusca. 



Occurrence. MONMOUTH FORMATION. Brightseat, Brooks estate near 

 Seat Pleasant, Friendly, 1 mile west of Friendly, ? McNeys Corners, 

 Prince George's County. 



Collection. Maryland Geological Survey. 



Superfamily MYACEA 

 Family CORBULIDAE 



Genus CORBULA Bruguiere 

 [Encyclopedic Methodique, 1792, pi. ccxxx] 



Type. Corbula gallica Lam. 



Shell small, thick, ovate, more or less rostrate ; valves unequal, the left 

 usually the smaller and the flatter; umbones prominent, prosogyrate or 

 erect, the right usually higher than the left ; hinge line of right valve fitted 

 with a single prominent tooth in front of the resilial pit ; lateral laminae 



Etymology: Corbula, a little basket. 



