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TERTIARY FAUNA OF FLORIDA ^ -^ 



This very rare and remarkable shell is almost invariably so eroded and 

 decayed as to obscure its characters. It is very oblique, flattened, angular in 

 front, with twenty-four flattened, longitudinally striate ribs separated by shal- 

 low channels on the disk, with the posterior area smooth and sculptured by 

 about eight radial very narrow grooves. Near the beaks the channels are 

 cross-striated. The hinge is strong, with the anterior minor cardinal un- 

 usually well developed, and an oblong pseudolunule on the hinge-margin exter- 

 nally above it. The characteristics of this shell, except its compression and 

 anterior wing, ally it to Dinocardium, but it is almost worthy of a section to 

 itself. 



Cardium (Cerastoderma) leptopleura Conrad. 



Cardimn leptopleura Conrad, Fos. Medial Tert., p. 66, pi. 37, fig. 5, 1845 ; Proc. Acad. 

 Nat. Sci. Phila., i., p. 29, 1841. 



Miocene of Plum Point, Maryland ; Burns. 



Shell resembling the C. waltonianwn, but thinner, less inflated, with the 

 anterior part of the basal margin less rounded and produced; ribs lower than 

 in C. craticidoide and the shell more triangular and oblique; the tops of the 

 ribs are keeled, but the keel is not sharp or angular, but squarely flattened 

 like the edge of a board ;• the ribs number from thirty-one to thirty-seven in 

 different individuals, — thirty-three appears to be the most common number, — 

 but the shells are very poorly preserved and always more or less eroded. 



I have identified these Plum Point shells with Conrad's C. leptopleura, 

 although their correspondence with his figure left something to be desired, 

 because in a general way his description fits them as far as it goes, and no 

 shell agreeing perfectly with his figure has been collected even in his original 

 locality after careful search. Should the present form be found to be sepa- 

 rable I would suggest for it the name of Cardiiini leptopleura variety uiary- 

 landicum. 



Cardium (Cerastoderma) tseniopleura n. sp. 

 Plate 49, Figures i, 2. 

 Miocene of Yorktown, York River, and Suft'olk, Nansemond River, Vir- 

 ginia; Burns and Harris. 



Shell thin, oblique-ovate, inequilateral, with moderately elevated beaks; 

 sculptured, with thirty-one to thirty-four narrow, elevated ribs with the sec- 

 tion of a T-rail, separated by wider, not channelled interspaces ; the rounded- 

 flattened overhanging tops of these ribs are crossed by concentric sculpture 



