Synopsis Fresh-Water Moeeusca 

 Subgenus TRUNCILLA s. s. 



8i 



Fig. 217 



Shell covered with broken rays, somewhat triangular and without a wide, 

 radiate, posterior furrow. 



Type: T. triquctcr Raf., fig. 217. Animal, fig. 218. 



Subgenus SCALENARIA (Rafinesque, 1820) Agassiz. 



Fig. 219 



Male shell having a wide, radiating, shallow depression in front of the 

 posterior ridge ; that of the female having a small, rounded, well-defined, 

 radial post-'basal swelling. 



'J'yi>c : Unio sulcatus Lea, fig. 219. 



