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641 

 TERTIARY FAUNA OF FLORIDA . ^ 



fifty in all, subvertical, shorter in the middle of the hinge ; margins of the 

 valve deeply fluted; right valve with wider interspaces and narrower, often 

 tripartite, ribs. Lon. 40, alt. 28, diam. 30 mm. 



This fine shell has a neat and elegant surface sculpture, and is one of 

 several which the Oak Grove marl contains and which appear to be new. 



Scapharoa (Scapharca) santarosana n. s. 

 Plate 31, Figures 2, 10. 



Oligocene of the Chipola River marl, of the lower bed at Alum Bluff, 

 of the Sopchoppy limestone, and of the Oak Grove sands, Santa Rosa County, 

 Florida; Burns and Dall. 



Shell small, short, plump, rostrate, with moderately elevated, mesially 

 sulcate prosocoelous beaks ; left valve with thirty elevated, squarish, radial 

 ribs, separated by slightly narrower channelled interspaces ; the ribs on the 

 posterior slope are low, smaller, and nearly smooth ; those on the middle of 

 the shell have mostly near the margin a shallow mesial sulcus ; in those still 

 more anterior the sulcus is deeper and wider, dividing each rib over most of 

 its length into two more or less rounded riblets ; concentric sculpture of regu- 

 larly spaced elevated lines, which on the ribs appear as prominent ripples ; 

 right valve having the ribs narrower and less strongly sculptured, and the 

 sulci less distinct ; cardinal area short, with about three concentric grooves ; 

 beaks within the anterior fourth ; hinge-line short, with about fifty-seven rather 

 irregular, closely adjacent, nearly vertical teeth, longer and more oblique dis- 

 tally ; margins strongly fluted ; base flexuous, posterior end narrow, pointed, 

 without any marked angle at the end of the hinge-Une. Lon. 36.5, alt. 28, 

 diam. 28 mm. 



This species is most nearly related to A. staviinata Dall, fi-om which it 

 can be distinguished especially by its lower beaks, more oblique posterior 

 slope, more flexuous base, and attenuated posterior end. 



Scapharoa (Scapharca) staminata n. s. 

 Plate 31, Figures ii, 13. 

 Oligocene of the lower bed at Alum Bluff, and perhaps at Roberts, 

 Escambia County, Florida. 



Shell of moderate size, plump, rhombic, with well-elevated, hardly 

 sulcate, slightly prosoccelous beaks, situated in the anterior third of the 

 length ; left valve with twenty-eight or twenty-nine radial ribs, the posterior of 



