FREE INSTITUTE OF SCIENCE 



975 



TERTIARY FAUNA OF FLORIDA 



times present, is a rare and uncertain character in the recent species I have 

 examined. The posterior tooth which lies on the anterior end of the nymph 

 is usually very slender or obsolete, and often only slight if any traces of it 

 remain. In the small species the posterior tooth of the right valve is usually 

 entirely absent. The genus Psammobia will fall naturally into two subgenera 

 and several sections, as follows : 



Subgenus Psammobia s. s. Type 5 1 . feroensis Gmel. 



Shell elongated, more or less pointed behind, compressed, somewhat rudely 

 concentrically sculptured, the posterior dorsal area frequently sculptured di- 

 versely from the disk, the pallial sinus elongated and, for the most part, coales- 

 cent below with the pallial line. 



Section Garuin Dall (Gari Cossmann non Schum.). 



Shell telliniform, concentrically grooved, the pallial sinus short, detached 

 from the pallial line for about half its length or more, not deeper than the 

 vertical of the beaks. 



As Cossmann has named no type, Psammobia Dutemplei Desh. of the 

 Parisian Eocene may be selected. 



Section Psammoica Dall (Soletellina Cossmann, not Blainville). 



Shell small, Angnlus-like, smooth, flattish, and pointed behind ; the hinge 

 with two teeth in each valve, the pallial sinus elongated and coalescent below 

 with the pallial line. 



This differs from Psammobella most obviously in its compressed and more 

 tellinoid form. Type P. appendiculata Desh. of the Parisian Eocene. 



Section Psammodonax Cossmann. Type P. caillati Desh. 



Shell small, compressed, short, and often angular behind with radial striae 

 on the posterior dorsal area, the left valve with two teeth, the posterior feeble 

 or obsolete, pallial sinus short, oval, and wholly free from the pallial line. 



The striae are found in many species of different sections ; most recent ones 

 show traces of them. 



Section Grammatomya Dall, 1898. Type P. squamosa Lam. 

 Shell with strong oblique sculpture, not interrupted at the borders of the 

 posterior dorsal area ; two teeth in each valve ; sinus rounded, short, and more 

 or less detached in front from the pallial line. This is Gari Fischer, 1887, not 

 Schum., 1817. 



