FREE INSTITUTE OF SCIENCE 

 TERTIARY FAUNA OF FLORIDA 



confirmed. /'. imperils belongs to the section Chlamys and, though with very 

 similar sculpture, is a more elevated and less rotund species. Worn speci- 

 mens of perplanus which have lost the scaly sculpture have a very different 

 aspect and are often puzzling. A variety has the threads with minute crowded 

 scales, while the tops of the ribs arc smooth, giving them a laterally fringed 

 appearance; these specimens have twenty-two ribs only. This form was 

 obtained at the Natural Bridge, Alachua County, Florida, and in the lower 

 bed (Hawthorne horizon) at Hawkinsville, Georgia, by Burns. 



Pecten (perplanus var. ?) centrotus Oall. 

 PLATE 34, FIGURE 21. 



Eocene (Vicksburgian ?) of the Ponce de Leon artesian well, St. Augus- 

 tine, Florida, at a depth of two hundred and twenty-five feet; Willcox. 



Shell like the preceding, with twenty-three flat-topped smooth ribs with 

 lateral fringes which wholly fill the interspaces but do not unite in the middle 

 of the channel. Two or three of the ribs near the middle of the disk show 

 six to eight distant, regularly spaced short spines projecting from their tops; 

 the other ribs are destitute of spines. Interior sharply and deeply grooved 

 to correspond with the external ribs. Alt. 2O, lat. 18.5 mm. 



The single valve obtained is somewhat defective, but its sculpture is so 

 different from any of the other forms that it seemed best to describe it. 



Pecten (^Equipecten ?) choctavensis Altlrich. 

 l\\-tt'>i tlun'tavi-nsis Aldrich, Harr. Bull. Pal., ii., p. 68, pi. 5, fij;. 7, 1895. 



Eocene of Wood's Bluff, Choctaw County, Alabama; Aldrich. 



This shell when not worn has a very flat imbricated sculpture over-all, 

 pointed on the backs of ribs and riblets, the surface on the interspaces being 

 quincuncially microscopically punctate. It is rather flat for an sEquipectcn, 

 and is one of the many peripheral species uniting the different sections. 



Pecten (.SDquipecten) chipolanus n. s. 



1'l.ATK 21). KlCURK Q. 



Upper Oligocene of the Chipola marls, lower bed at Alum Bluff, and the 

 silex beds at Ballast Point, Tampa Bay, Florida ; Dall and Burns. 



Shell solid, rounded, plump, with fifteen to seventeen strong, rounded ribs 

 with narrower interspaces which arc almost channelled, both ribs and chan- 

 nels with continuous fluctuated, sometimes crowded, low concentric lamellae ; 



