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14.27 



TERTIARY FAUNA OF FLORIDA 



Shell inequilateral, broad ovate, .with small, rather low beaks ; anterior end 

 short, rounded, posterior longer, arcuate dorsally, broadly rounded behind ; base 

 gently arcuate ; sculpture of about twenty-five simple, low, subequal ribs, sepa- 

 rated by wider, shallow, unchannelled interspaces; lunule small, impressed; 

 hinge normal, basal margin internally fluted. Length 17.5, height 14.0, diameter 

 9.0 mm. 



At first glance this species recalls a very much worn young alticostata, but 

 an examination shows the surface to be intact and the sculpture naturally as 

 described. 



Venericardia prsecisa n. sp. 



PLATE 56, FIGURES 7, 8. 

 Venericardia rotunda Lea var. Harris, Ann. Rep. Geol. Surv. Ark. for 1892, ii., p. 149, 1894. 



Jacksonian Eocene of Cleveland County, Arkansas, at Station 2232, S. 32, 

 T. 10, R. n W.; G. D. Harris. 



Shell thick, small, rounded, with small, rather anterior not elevated beaks ; 

 sculptured with about thirty-four narrow, uniform, articulated ribs, with a 

 T-rail section, separated by about equal V-shaped interspaces with no accom- 

 panying threads or riblets ; the articulation of the ribs is close, even, fine, and 

 squarely nodular, flat and polished above ; the posterior slope has the nodules 

 more elevated and longer with their short slopes ventrally directed ; there are 

 on the average three to five articular nodes in a millimetre's length of rib ; 

 lunule small, convex; beaks situated about the anterior third; hinge heavy, 

 inner margins elaborately and deeply fluted. Length 13.0, height 12.5, diameter 

 8.5 mm. 



This differs from V. tetrica in having lower and more compact ribbing, 

 with the tops of the ribs flattened, widened, and polished. In tetrica the beaks 

 are higher, more prominent, more anterior, and the sculpture more rasplike. 



Venericardia carsonensis n. sp. 



PLATE 56, FIGURE 9. 



Carson's Creek and Red Bluff Eocene of Wayne County, Mississippi; 

 Burns. 



Shell somewhat squarish, rounded, moderately inflated, thin, with about 

 nineteen to twenty-one very narrow, elevated radial ribs, separated by much 

 wider interspaces ; sculpture imbricate-nodulous, the nodules in perfect speci- 

 mens becoming irregularly spinose in the posterior third of the shell; the 

 nodules are not so close to each other as in V . tetrica and V. prcecisa as a rule, 



