FREE INSTITUTE OF SCIENCE 



1420 



TERTIARY FAUNA OF FLORIDA 



Oligocene silex beds of Ballast Point, Tampa Bay, Florida; Dall, Burns, 

 Willcox, and Shepard. Also at Bailey's Mill Creek Sink, in Jefferson County, 

 Florida. 



This species is abundant in the locality referred to, where it is represented 

 by silicious pseudomorphs often beautifully reproducing the most delicate sculp- 

 ture of the original shell. The sculpture recalls that of V. perantiqua, but the 

 lateral terraces of the ribs are less pronounced and often absent. The hinge 

 is that of normal Venericardia and not of Carditamera. 



The species of this group from the Midway to the Chattahoochee are as 

 follows, a new though allied type of notably robust habit taking up the line in 

 the superincumbent formations : 



f Bowden V. scabricostata. 



Oligocene \ Chattahoochee V . serricosta. 



[ Vicksburgian V . vicksburgiana. 



Red Bluff V . carsonensis. 



Jacksonian V . tetrica. 



I (Cleveland County, Arkansas) V. pracisa. 



Eocene J 



Claibornian V ' . rotunda. 



Chickasawan V . complexicosta. 



Midwayan . . . . V. perantiqua. 



A species belonging in this group appears in the black shales of the Isthmus 

 of Panama at Gatun, but the condition of my specimens is not good enough 

 to warrant naming them. 



Venericardia hadra n. sp. 



PLATE 53, FIGURES n, 13. 



Oligocene of the Chipola horizon on the Chipola River and at Alum Bluff 

 on the Chattahoochee River, Calhoun County, Florida ; Burns and Dall. 



Shell solid, robust, obliquely oblong, the beaks full, prominent, prosogyrate, 

 and nearly anterior ; anterior side short, bluntly rounded, posterior side longer, 

 compressed, roundly subtruncate behind; sculpture of about nineteen radial 

 ribs, of which the posterior five or six are smaller and less elevated than the 

 others ; anterior ribs stout, sometimes with a thread or terrace laterally, the 

 summit articulated rather sparsely with small, squarish, transverse nodules, 

 which have a tendency to become obsolete behind and below; interspaces nar- 

 rower than or subequal to the ribs, partially channelled ; lunule extremely small 



