58 



Bryant Walkkr 



zagged ; surface of the shell covered with oblique folds and wrinkles ; epi- 

 dermis dark olive, shining; left valve with two elongated, compressed pseu- 

 docardinals, the posterior under the beak and curved upwards, cutting off 



Fig- 173 



the hinge plate in the right valve, which has a single, compressed pseudo- 

 cardinal in front; laterals numerous, short, blurred; nacre Vv^hite. ]\Iar- 

 supium occupying the outer gills. 



Fig. 1 7-1 

 Type: Alasmodonta confragosa Say, fig. 173. Animal, fig. 174. 



Genus ARKANSIA Ortmann and Walker, 191 2. 



Shell moderately thick, subrotund to subovate or subrhomboidal, in- 

 flated, with full beaks. Disk sculptured with irregular, oblique folds, which 

 are sometimes indistinct. Beak sculpture poorly developed, consisting of 

 two to three double-looped bars, the loops slightly swollen or tubercular, dis- 



