PELECYPODA—TELEODESMACEA. 



569 



CLXX. Cumingia Sowerby. 



Small, thin, oval, rounded anteriorly, somewhat wedge-shaped 

 posteriorly. One small cardinal tooth in each valve. Right valve 

 with two strong lateral teeth ; left valve with extended dorsal mar- 

 gins to fit in the channels above the laterals of the right valve. 

 These dorsal extensions form a lunule and escutcheon which are 

 thus nearly confined in the left valve. Surface marked with radi- 

 ating striae. Concentric lines fine or lamellose. Resilifer spoon- 

 shaped. Pallial sinus deep and wide. 



Habit nestling, i. e. y though not excavating burrows they occupy 

 those made by true borers. Eocenic-Recent. 



Fig. 780. a, Semele subovata, right valve ; b, c, Cumingia medialis, left valve, 

 exterior and interior views. (Md. Survey.) 



580. C. medialis Conrad. (Fig. 780, b, c.) Miocenic. 



Anterior portion of shell inflated ; posterior depressed. Resilifer 

 prominent, projecting. 



Maryland (Choptank), Virginia, North Carolina, South Carolina. 



CLXXI. Siliqua Megerle von Muhlfeld. 



Shell flattened, straight. Hinge line feeble with one right and 

 two left vertical cardinal teeth and in each valve a posterior hori- 

 zontal tooth. An internal rib runs vertically from the beak. 

 Cretacic-Recent. 

 581. S. huerfanensis Stanton. (Fig. 781.) Cretacic. 



Shell thin. Average length 2 inches. Interior rib runs 



-^ ^?^^a^^ p. 



Fig. 78] 



Siliqua huerfanensis, internal mold of right valve retaining portions of 

 shell and showing pallial sinus. (After Stanton. ) 



