TRANSACTIONS OF WAGNER 

 986 



TERTIARY FAUNA OF FLORIDA 



feeble ; left valve with feebler laterals, the posterior cardinal slender ; right 

 valve with well developed laterals, cardinals subequal, entire ; pallial sinus 

 large, rounded, obliquely ascending, free of the pallial line. 



Section Semelina Dall. Type 5". nuculoides Conrad. 



Shell small, nuculiform ; sculpture uniform, close, concentric ; chondro- 

 phore short; left valve without distinct laterals, the dorsal margins fitting 

 above the laterals of the right valve ; left posterior cardinal absent or obsolete, 

 the anterior cardinal bifid ; otherwise as in Semele s. s. 



The species of this section are very similar to one another, and have ex- 

 tended from the Oligocene through all the Tertiary horizons to the present 

 fauna. For this reason it seems worthy of sectional rank. The characters by 

 which the shell differs from Semele proper are only such as are usually corre- 

 lated with diminished size. 



The Eocene species are S. linosa Conrad, a fine, large, thin, concentrically 

 sculptured species very much like some recent ones, but very rare at Claiborne ; 

 and 5". profunda Conrad, also from the Claibornian, which is a small, smooth 

 species, conchologically near to Abra but having the characteristic Semele out- 

 line. Both these species are figured on supplementary plate 19 of Harris's 

 reprint of Conrad's " Fossils of the Tertiary Formations," but S. profunda has 

 never been described. 



In the Lower Oligocene (Vicksburgian) are known S. mississippiensis 

 Conrad,* a smooth, very equilateral shell ; and perhaps another described by 

 Conrad from the same horizon at Vicksburg under the name of Corbis staminea. 

 The fauna of the Upper Oligocene is better explored or richer in species of 

 this group. 



Semele chipolana n. sp. 



PLATE 37, FIGURE 3. 



Upper or Chipolan Oligocene at the base of Alum Bluff, Florida, also at 

 Bailey's Ferry (now the county bridge) and McClellan's farm, on the Chipola 

 River, Calhoun County, and in the Oak Grove sands at Oak Grove, Santa 

 Rosa County, Florida. 



Shell large, solid, rather inflated, nearly equilateral, slightly inequivalve; 

 beaks low, adjacent; anterior end longer, sloping above, rounded in front and 

 below into the arcuate base ; posterior end high, bluntly rounded, subtruncate 



* A specimen, apparently of this species, with the manuscript name of 5. perovata 

 Conrad, is in the collection of the Academy of Natural Sciences, Philadelphia. 



