TRANSACTIONS OF WAGNER 

 638 



TERTIARY FAUNA OF FLORIDA 



This species has the appearance of being the Oligocene ancestor of the 

 Miocene A. licnosa, from which it differs by its smaller size, closer and rather 

 narrower ribbing. 



Scapharca (Scapharca) latidentata n. s. 

 PLATE 36, FIGURE 15. 



From the Oligocene of Ballast Point, Tampa Kay, of the lower bed at 

 Alum Bluff, and in the Chipola marls of Florida, and probably from the Oak 

 Grove sands in western Florida. 



Shell small, ovate, moderately convex, with low, quite anterior, mesially 

 sulcate, prosoccelous beaks ; left valve with about thirty rounded, radiating, 

 undivided ribs, separated by slightly wider interspaces, and crossed by 

 numerous smaller concentric ridges which become beatllike on the ribs and 

 vary in prominence in different specimens; base evenly arcuate, ends rounded ; 

 cardinal area narrow, impressed, smooth, with one or two grooves behind 

 the beaks, but none elsewhere; valves slightly twisted, so that the basal 

 margin is not in a single plane; line of teeth interrupted a little behind the 

 beaks, the anterior series having the anterior and posterior teeth larger and 

 the intervening teeth thinner and more closely adjacent, all nearly vertical ; 

 posterior teeth vertical, shorter, the series longer, the teeth smallest proxi- 

 mally and regularly increasing in size towards the distal end of the series, 

 equidistant and regular; inner margin of the valve deeply fluted. Lon. 18, 

 height 1 1, diain. 9 mm. 



This little shell looks a good deal like the young of Anadara aresta 

 Ball, but has the beaks less central, less prominent, and distinctly impressed 

 mesially, giving a somewhat bilobed aspect to the very young. 



Scapharca (Scapharca) callicestosa n. s. 

 PI.ATK 34, FIGURES 17, 18. 



Upper bed (Miocene) at Gaskin's Wharf, on the Nansemond River, sixteen 

 miles below Suffolk, Virginia ; F. Burns. 



Shell of moderate size, rather thin, rhomboidal, with small, prominent, 

 mediosulcate, prosoccelous beaks situated at about the anterior third of its 

 length ; left valve with about thirty-seven squarish subequal radial ribs, sepa- 

 rated by narrower channelled interspaces ; on the tops of these ribs are four 

 longitudinal threads, the inner pair larger and more prominent but separated 

 by a somewhat deeper sulcus than those external to the inner threads ; con- 

 centric sculpture of fine, close, rounded, slightly elevated threads, which over- 



