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TERTIARY FAUNA OF FLORIDA yj 



behind narrower and with more numerous foliations ; the identity of the con- 

 centric ribs not so much lost in confluence ; the beaks closely ribbed to their 

 apices, and the escutcheon somewhat smaller. A specimen intact measures : 

 length 30, height 23, diameter 15 mm., but fragments show that it attains a 

 larger size at times. The age of the beds from which it comes is certainly 

 Oligocene in the last instance ; whether the others are older or not is not yet 



positively known. 

 i 



Chione (Lirophora) ballista n. sp. 



PLATE 55, FIGURE 23. 



Oligocene silex beds at Ballast Point, Tampa Bay, Florida ; Crosby, Burns, 

 and Dall. 



Shell rather small, arcuate-trigonal, with small, acute umbones, and from 

 eight to ten heavy concentric recurved ribs, not confluent but bent backward 

 and attenuated near the posterior dorsal border ; lunule narrow, striated, small ; 

 also the escutcheon ; obsolete radial striation sometimes visible on the ventral 

 side of the larger ribs, but not in the interspaces ; anterior and posterior ends 

 often but not always pointed ; base and posterior dorsal border arcuate ; in- 

 terior normal. Length 24.0, height 19.5, diameter 12.0 mm. 



This species is apt to be confounded with Artena glyptoconcha, of the same 

 horizon, unless attention is called to the absence of the minute anterior lateral 

 on the hinge, and of the fine concentric striation in the Chione. It considerably 

 resembles the next species, which, however, has more numerous and basally 

 punctate ribs, which are pinched off at about the posterior third of the shell, 

 while in this species the attenuation is less and is close to the dorsal margin. 



Chione (Lirophora) Hendersonii n. sp. 



PLATE 55, FIGURE 22. 



Venus paphia Guppy, Quart. Journ. Geol. Soc. London, xxxii., p. 530, 1876; Geol. Mag., 

 Dec. 2, vol. i., p. 450, 1874, etc., ex parte. 



Oligocene of the Bowden marl at Bowden, Jamaica, Henderson and Simp- 

 son, and of Haiti, Guppy. 



Shell resembling the last species, but with about fifteen ribs on the ventral 

 bases, of which the radial sculpture is represented by a series of punctuations 

 which are rarely drawn out into striae ; the ribs are closer together, sometimes 

 obscuring the interspaces ; the imaginary line at which the thick ribs suddenly 

 become very thin and elevated marks off the posterior third of the shell, more 

 than in any other species noted ; the foliations are very thin and were pre- 



