TRANSACTIONS OF WAGNER 

 838 



TERTIARY FAUNA OF FLORIDA 



with a more or less prominent process upon which the resilium and ligament 

 are inserted, in front of a socket into which the cardinal tooth of the right 

 valve fits; the posterior margin of this socket is sometimes elevated like an 

 indistinct tooth ; beaks prominent, prosogyrate or erect, the right one usually 

 superior to the left; sculpture variable, often discrepant on the two valves, 

 rarely reticulate, and never strongly radial ; pallial line with a small sinus or 

 none ; lunule and escutcheon usually absent ; ligament chiefly internal ; siphons 

 complete, usually short, and fringed distally; mantle with a pedal opening but 

 mostly closed ventrally. Chiefly marine. 



Section Corbula s. s. 



Shell subtrigonal, ligament internal ; globose ; valves feebly concentrically 

 sculptured with no rostral keels, sculpture discrepant on the two valves. 

 Type C. gallica Lam. Bicorbitla Fisher is identical. 



Section slloiilis Megerle. 



Like Corbula, but with strong concentric sculpture and keeled rostrum. 

 Type C. sulcata Lam. (+ A. gniitcensis Meg.). 



Section Lcntidium C. and J. 



Shell compressed, trapezoid, feebly concentrically sculptured ; the liga- 

 ment appearing externally through a fissure in the right mnbo. Type C. 

 mcditerranea Costa. Corbuloinya Nyst is identical. Recent and Tertiary. 



Section Cidit'oiorlnila Cossmann. 



Shell elongate ovoid, with two elevated radial keels on the rostrum, 

 which is distally truncate; the valves similarly sculptured. Type C. biangnlata 

 Deshayes. Recent and Tertiary. 



This group may be extended to cover the American species with similarly 

 sculptured valves, like C. contracta Say, in which the keels are less pronounced 

 and the dorsal one sometimes obsolete. 



Section Tiza ilc ( '.rr^orio, 1890. 



Shell very inequilateral, twisted, and produced behind, the right valve 

 convex, the left flattened or even concave, pointed behind ; surface smooth, 

 valves similarly sculptured, pallial sinus obsolete. Type C. alta Conrad, 

 Journ. Acad. Nat. Sci. Phila., 2d Sen, ii., pi. i, fig. 3, 1850 (not i., pi. 12, figs. 



