CONCHOLOGIA CESTRICA. 10$ 



Shell, heavy, oblique, inflated, anterior side longest, 

 narrower, sub-angular; beaks posterior, full, prominent, 

 distant ; valves solid ; striae regular, distinct ; epidermis 

 glossy, variable, straw, greenish, or yellowish, zoned ; 

 hinge margin elevated ; cardinals small, united ; laterals 

 strong, distinct, short. H. 4^, W. 5, T. 4, mill. 



Station, streams and rivulets. Chester County; 

 abundant. 



P. abditum, HALDEMAN, Proc. Acad. Nat. Sci., I., 1841. 



JP. abditum. [Prime.] 

 Tig, 207. 



Shell, round-oval, moderately convex, margins well 

 rounded ; beaks posterior, small ; smooth, straw color ; 

 hinge margin nearly straight; cardinal teeth small, 

 separate, the anterior larger, and more prominent; 

 laterals small, not elongated. H. 3^, W. 4, T. 2, mill; 



Station, streams, fountains, and rivulets. Chester 

 County; frequent. 



