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1275 



TERTIARY FAUNA OF FLORIDA ' ^ 



narrower interspaces, and with rather distant, slightly elevated, thin crenulate 

 concentric lamellae ; lunule lanceolate, small and narrow ; escutcheon defined 

 by a deep sulcus, on the left valve almost linear, on the right wider but usually 

 defective in the fossils ; hinge normal* anterior lateral small and pustular ; 

 pallial sinus small, short, ascending, rounded in front; basal inner margin 

 minutely crenulate. Length 49, height 41, diameter 26 mm. 



This species, though similar in a general way to the young of the large 

 species like C. Listen Gray, of which it is the precursor, never attains a large 

 size, the measurements given being taken from a fully adult specimen. It is 

 not uncommon at Ballast Point and is chiefly notable for the regularity of its 

 radial sculpture and the thin and distant concentric lamellae. 







Cytherea csesarina n. sp. 

 PLATE 53, FIGURE 5. 



Oligocene of the Chipola marl, Calhoun County, Florida, Burns ; and of 

 White Beach near Osprey, Florida, Dall. 



Shell ovate, inequilateral, the beaks being in or at the anterior fourth lunule ; 

 hardly impressed, concentrically striate, cordate, small ; escutcheon long and 

 narrow, wider in the right valve, bordered on each valve with a strong sulcus, 

 the ligament hidden by' the right-hand portion ; sculpture of numerous narrow, 

 elevated, thickened, concentric lamellae, somewhat reflected and with narrower 

 concentrically striate interspaces ; these cross fine radial riblets, which are 

 distinct and uniform on the young shell but rapidly become obsolete, though 

 the broad tops of the concentric sculpture are crenulate or, more strictly 

 speaking, articulated by the development on them of channels or sulci corre- 

 sponding to those of the obsolete riblets; hinge strong, the larger cardinals 

 deeply bifid, the anterior lateral small and pustular ; pallial sinus small, ample, 

 short, rounded in front; inner basal margins minutely crenulate. Length of 

 figured valve 66, height 58, double diameter 40 mm.; length of an internal 

 cast from White Beach 75, height 60, diameter 42 mm. 



This fine species is quite distinct from any of the others ; the radial sculp- 

 ture, contrary to usage, is more distinct in the middle of the disk than on the 

 distal portions of the shell. It much more nearly resembles the recent west 

 American C, multicostata Sowerby than any species now living on the Atlantic 

 side, and adds in this way an interesting item to the list of those which indicate 

 more or less clearly a tolerably close connection between the two faunas in 

 Oligocene times. 



