Synopsis Frush-Wate;r Mollusca 



79 



with one or two pseudocardinals and one lateral in the right valve, and 

 two pseudo-cardinals and two laterals in the left; female shell having a 

 strong inflation of the shell and dilatation in the post-basal region, produc- 

 ing a distinct posterior truncation of the shell. Marsupium kidney-shaped, 



Fig. 214 



-^ an 



i^ig. 215 



occupying the posterior part of the outer gills ; edge of the mantle of the 

 female in front of the branchial opening developed into a ribbon-like flap, 

 generally produced anteriorly into a full, projecting lobe, which has a lacer- 

 ated appearance. 



Type: Unio ovahis Say, fig. 214. Animal, fig. 215. 



