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1241 



TERTIARY FAUNA OF FLORIDA 



Shell small, only moderately convex, subtrigonal, inequilateral, polished, with 

 shallow, concentric sulci, less marked in the centre of the disk, diminishing in 

 number and increasing in strength towards the anterior end of the shell ; beaks 

 small, erect, acute at the anterior third ; lunule narrow, lanceolate, as long as 

 the anterior dorsal slope, slightly impressed, smooth, defined by an impressed 

 line ; escutcheon not defined ; hinge compact, the anterior left cardinal bifid ; 

 the sulcations of the margin well marked but not as dense as in the larger 

 species ; the sinus deep, narrow, rounded in front. Length 7.0, height 5.0, 

 diameter 2.5 mm., but usually smaller. 



This is the earliest and smallest species, notable for its acute beaks. These 

 shells vary, some being shorter and higher, others more beaked and elongate. 

 All the species vary in much the same way, but, in spite of the difference in 

 outline, there is a recognizable facies to each. Only one or two species occur 

 in any single horizon. 



Transennella chipolana n. sp. 

 PLATE 57, FIGURE 6. 



Oligocene of the Chipola River, Florida, at McDonald's Ranch ; Dall. 



Shell small, short, ovate-trigonal; beaks low, anteriorly directed, near the 

 anterior third; anterior dorsal slope short, straight, with a narrow, cordate, 

 slightly impressed lunule; posterior slope convexly arcuate, posterior end 

 rounded, base evenly arcuate ; surface covered uniformly with fine, close, sharp, 

 concentric grooves; hinge and margins normal; pallial sinus ample, deep, 

 rounded in front. Length 5.0, height 4.2, diameter 2.0 mm. 



Only a single valve of this species was obtained, but it is well distinguished 

 by its fine, even sculpture, Chionella-like outline, and ample' sinus. 



Transennella santarosana n. sp. 

 PLATE 57, FIGURE 13. 



Oligocene sands of Oak Grove, Santa Rosa County, Florida ; Burns. 



Shell small, plump, subtrigonal, polished, and sculptured with numerous 

 slightly irregular concentric sulci; beaks small, subcentral, slightly anteriorly 

 directed; lunule cordate, narrow, bounded by an impressed line, striated; hinge 

 with the middle cardinals and the anterior lateral large and conspicuous ; pallial 

 sinus wide, short, rounded, not reaching the middle of the valve. Length 6.5, 

 height 5.5, diameter 3.8 mm. 



This is easily distinguished from T. chipolana by its less sharp and crowded 

 sculpture and its more convex valves. 



