Synopsis Fresh-Water Moli.usca 

 Subgenus ALASMINOTA Ortmann, 1914. 



61 



Shell elongated elliptical, rather small. Surface without sculpture. 

 Pseudocardinals delicate ; laterals nearly or quite wanting. Beak sculptun; 

 not heavy, consisting of four to six rather fine, sharp bars, the first one or 



Fig. 178 



two subconcentric, the following ones sharply double-looped, the posterior 

 loop smaller, separated from the anterior by a deep, sharp, re-entering angle. 



Type: Afai'cjarifav.n Iwhtonia Lea, fig. 178. 



Subgenus PTEROSYNA Rafinesque, 183 1. 



Shell large, ovate-rhomboid, inflated in the post-basal region; beaks 

 much compressed; their sculpture sharply and strongly doubly looped; epi- 

 dermis dark, scarcely rayed ; teeth very heavy. 



Fig. 179 

 Type: /llasniodoiita rniuplaiiala Bn.r., i\g. 179. 



