52 



Bryant Wai^ker 



Section ELLIPTIC s. s. 



Shell elongated, rhomboid or oval, usually more or less biangulate be- 

 hind: beak sculpture consisting of a few rather strong ridges, which are 

 nearly parallel to the growth lines or slightly doubly looped; the surface 

 smooth or feebly corrugated. 

 Type: Unio a^assideiish^m., fig. i6i. Animal, fig. 162. 



Fig. 161 



-,an 



Fig. 162 

 Section CANTHYRIA Swainson, 1840. 



Fig. 163 



Shell inflated, suboval, spinose, 

 with a high, rather sharp posterior 

 ridge, above which it is somewhat 

 truncated ; beaks rather compress- 

 ed ; epidermis smooth and shining, 

 variegated with angular blotches ; 

 linge sharply curved at the cen- 

 tre; pseudocardinals rather com- 

 pressed ; laterals short, remote ; 

 beak cavities rather deep. 



Type: Ujiio spinosus Lea, fig. 163. 



