1267 



Pitaria (Hyphantosoma) floridana n. sp. 

 PLATE 54, FIGURE 10. 



Oligocene marl of the Chipola horizon at Alum Bluff and on the Chipola 

 River at McDonald's farm ; Dall and Burns. 



Shell subtrigonal, solid, nearly equilateral, sculptured with fine, close, con- 

 centric wrinkles, over and upon which is imposed the faint, close, zigzag sculp- 

 ture of divaricate lines with numerous angles ; anterior dorsal slope nearly 

 straight, posterior gently arched, with one or two faint radial ridges indi- 

 cated as extending from the umbo to the posterior margin ; lunule long, rather 

 narrow ; hinge delicate, anterior lateral prominent, compressed ; posterior 

 right cardinal bifid near the dorsal end ; grooves of the dorsal margin deep ; 

 anterior end rounded ; posterior end obscurely truncate, base produced a little 

 in the middle. Length 29.2, height 24.0, diameter 17.0 mm. 



Young shells were abundant in the marl, full-grown ones comparatively 

 scarce. 



Pitaria (Hyphantosoma) opisthogrammata n. s. 

 PLATE 54, FIGURE 8. 



Pliocene marl of .Shell Creek and Alligator Creek, near Charlotte Harbor, 

 Florida ; Willcox and Burns. 



Shell rounded quadrate, produced and attenuated in front, subtruncate be- 

 hind, with a well-marked, wide, shallow sulcus extending from the beaks 

 backward and downward to the middle of the truncation ; beaks inflated, an- 

 teriorly twisted ; lunule deeply impressed, subcordate, defined by a sharply 

 incised line, with a second impressed but less conspicuous and regular line in 

 harmony with the lunular boundary and dividing the lunule into two subequal 

 parts ; surface concentrically striate, feebly on the middle of the disk and more 

 emphatically towards the ends of the shell ; the zigzag sculpture nearly obso- 

 lete but usually discernible on the smoother basal parts of the shell, and 

 stronger in some specimens than in others ; pallial sinus ample, linguiform, 

 reaching the middle of the shell, with the upper border nearly on a level 

 with the bases of the adductor scars; the hinge well developed, the anterior 

 lateral prominent, compressed, triagular. Length 39, height 32, diameter 

 22 mm. 



The impressed lunule is more conspicuously depressed in the adult than in 

 the partly grown shell and differs also in different specimens. 



