13 Aldrich, Eocene Fossils 13 



umbilicus. Interior nacreous. 



Height, 1.5 ; greatest diameter, 5 mm. 



Claiborne Sand, Claiborne, Ala. 



This little species may equal one of the species described 

 by DeGregorio, but all his species appear to be smooth. 



Neritina unidenta, n. sp. 

 Plate V, fig. 7, 8 



Shell smooth, rather small, showing the epidermis and 

 a few lines of growth underneath. The spire is worn off . 

 Shell rather quadrate : outer lip sharp, inner lip flattened, 

 callus reflected, pillar bearing one large tooth curving down- 

 wards into the interior. The color markings are retained, 

 composed of close-set, dark brown broken lines, the entire sur- 

 face being covered. 



Height 7 ; maximum diameter 8 mm, 



Woods Bluff horizon, six miles east of Thomasville, Ala. 



This is the first undoubted Eocene Neritina from Alaba- 

 ma, and is interesting because there is a living form in the 

 Coosa and Cahaba rivers of Alabama. 



Neritina pupa Lin. from Cuba has also a faint fold in- 

 side the pillar lip, which rapidly disappears, probably absorb- 

 ed. Neritina showalteri Lea has no dentition on the pillar. 



Argyrotheca dalli n. sp. 

 Plate V, fig's 9, ro 



Shell quite small ; dorsal valve oval, exterior with about 

 fourteen folds radiating from the beak. Surface covered with 

 fine lines, and also finely perforated ; within also finely perforat- 

 ed but the perforations do not seem to extend through the shell . 

 Median septum strong, elevated, reaching nearly to the base. 



Height 4 ; width 4.5 mm. 



