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I 369 



TERTIARY FAUNA OF FLORIDA 



Shell solid, high, short, laterally very convex, longitudinally subcompressed, 

 with large, moderately impressed, cordiform dorsal areas ; beaks small, narrow, 

 prosogyrate, with a small, globular, deeply excavated lunule, much larger pro- 

 portionately and more open in the young shell ; ligament very short ; surface 

 with little raised, flattish, concentric threads closely adjacent and with only 

 linear interspaces ; radial sculpture of four broad ribs separated by narrow, 

 shallow sulci, which become obsolete towards the base, and an impressed line 

 bordering the escutcheon ; the middle pair of ribs occupy about one-third of 

 the disk ; hinge strong, teeth conical, normal ; scars normal, inner margin of 

 the valves entire, except some very minute crenulations near the middle of the 

 base. Alt. 16.5, Ion. ii.o, diam. 15.0 mm. 



This is one of the most elegant species of the genus. The young, in which 

 the lunule is apparently much larger and more open, at first would be taken 

 for a distinct species. 



Section Cavilucina Fischer. 

 The Eocene species of this section have been already enumerated. 



Phacoides (Cavilucina) recurrens 11. sp. 

 Plate 52, Figure ii. 



Oligocene of the Bowden marls, Jamaica ; of the Chipola beds on the Chipola 

 River, and the lower bed at Alum Bluff on the Chattahoochee River, and the 

 silex beds at Miami, Florida. 



Shell small, flattish or only moderately convex, oblique, inequilateral, the 

 dorsal areas hardly indicated ; beaks small, low, prosogyrate over a small, mod- 

 erately impressed, rather narrow lunule ; posterior dorsal margin convexly 

 arched, as high as the beaks ; surface finely, concentrically, rather closely 

 grooved, with, towards the base, two or three deep, concentric sulci indicating 

 resting stages ; hinge-teeth small but distinct ; inner margins of the valves 

 minutely crenulate. Alt. 6.5, Ion. 5.7, diam. 4.0 mm. 



This little species is more like the recent West Indian P. blandus Dall than 

 the intervening colder water Miocene forms. 



Phacoides (Cavilucina) trisulcatus Conrad. 



Lucina trisulcata Conrad, Trans. Am. Assoc. Nat. and Geol., i., p. no, 1841 ; Am. Journ. 



Sci., xli., p. 346, 1841 ; Fos. Medial Tert, p. 71, pi. xl., fig. 5, 1845 ; Tuomey and 



Holmes, Pleioc. Fos. S. Car., p. 62, pi. xviii., figs. 18, 19, 1857 ; Holmes, Post-Pl. Fos. 



S. Car., p. 28, pi. vi., fig. 4, i860; Conrad, Proc. Acad. Nat. Sci. Phila. for 1862, p. 



