MEDINAN, NIAGARAN, AND CHESTER FOSSILS 
89 
Orth is dinorthis Foerste 
Orthis fissiplicata Foerste 
Hebertella fausta (Foerste) 
Hebertella fausta squamosa (Foerste) 
Hebertella daytonensis (Foerste) 
Platystrophia daytonensis (Foerste) 
Platystrophia reversata (Foerste) 
Dalmanella parva (Foerste) 
Dalmanella cf. eugeniensis Williams 
Rhipidomella h 3 ^brida (Sowerby) 
Triplecia ortoni Meek 
Platymerella manniensis Foerste 
Whitfieldella cf. cataractensis Williams 
Atrypa cf. marginalis (Dalman) 
Atrypa marginalis multistriata Foerste 
Atrypa laticorrugata Foerste 
Camarotoechia (Stegerhynchus) scobina (Meek) » 
Camarotoechia convexa (Foerste) 
Parastrophia sparsiplicata (Foerste) 
Stricklandinia triplesiana Foerste 
Leptaena center villensis Sp. nov. 
Plate XIV, fig. 11 
Pedicel valve 30 mm. long, 28 mm. wide at mid-length, 33 mm. 
wide along the hinge-line, the postero-lateral angles being acute. 
Valve moderately convex for a distance of 25 mm. anterior to 
the beak, and then rapidly descending toward the anterior margin 
for a nearly vertical distance of 15 mm. The more moderately 
convex part of the valve is concentrically wrinkled as far for- 
ward as 23 mm. anterior to the beak. The number of the wrin- 
kles varies from 11 to 16 in different specimens. The wrinkles 
are of approximately equal size anteriorly, becoming smaller 
and less elevated toward the beak. About 18 mm. anterior 
to the beak some specimens have a rather faint tendency toward 
a concentric downward curvature of the shell. The radiating 
striae are numerous, approximately of the same size, and number 
about 18 in a width of 5 mm. along the anterior slope of the shell. 
