FREE INSTITUTE OF SCIENCE 



62 t 

 TERTIARY FAUNA OF FLORIDA 



anterior margin nearly vertical from the hinge-line ; posterior end obliquely 

 truncate, the basal angle most extended, the dorsal one forming nearly a right 

 angle ; anterior teeth ten, posterior twenty-seven, with no noticeable hiatus in 

 the line, the teeth resembling those of A. paratina but proportionally larger; 

 interior smooth, the posterior end with a few flutings, the rest of the margin 

 entire ; the byssal foramen narrow and its margins encroaching only moder- 

 ately on the valves. Lon. 15, alt. of hinge-line 6, of beaks 8, diam. (greatest 

 posteriorly) 9 mm. 



This odd little shell is peculiar in being narrower near the very anterior 

 beaks and widest about the middle of the posterior slope. It appears to be 

 easily discriminated from the other species of this variable group known to 

 the region. 



Subgenus BARBATIA (Gray) Adams. 

 Section Calloarca Gray. 

 Barbatia (Calloarca) marylandica Conrad. 

 Byssoarca maryhwdica Conrad, Fos. Medial Tert. , p. 54, pi. 29, fig. i, 1840. 

 Barbatia marylandica Conr., Proc. Acad. Nat. Sci. Phila. for 1862, p. 580, 1863. 



Oligocene of the Ballast Point silex beds, Tampa Bay, the lower 

 (Chipola) bed at Alum Bluff, the Chipola marl of the Chipola River, Florida; 

 older Miocene of Jericho, Cumberland County, New Jersey; Middle Miocene 

 of Plum Point, Calvert Cliffs, and Centreville, Maryland; Willcox, Btirns, 

 Dall, and Harris. Possibly also in the Jacksonian. 



Careful comparisons of typical material show no specific differences 

 between the Miocene and Oligocene shells. 



Barbatia (Calloarca) irregularis n. s. 

 Plate 33, Figure 5. 



Oligocene of the silex beds at Ballast Point, Tampa Bay (fragment)? 

 Pliocene marls of Shell Creek, Alligator Creek, and the Caloosahatchie ; 

 Dall and Willcox. 



Shell thin, elongate, irregularly distorted; beaks prosogyrate; at the 

 anterior third rather low and compressed ; cardinal area long, rather narrow, 

 with very numerous (twelve) concentric grooves; surface irregular, sculptured 

 with numerous fine radiating, somewhat imbricated ribs, of which those in 

 front of the beaks and on the posterior dorsal slope tend to be larger and 

 more elevated ; there is a tendency to alternate or pair among the ribs in 

 some specimens; the imbrications or nodules on the ribs are somewhat 



