WAVERLT GROUP SPECIES. 313 



projection, below which the margin curves with a slightly convex out- 

 line obliquely backward and downward sometimes nearly to the middle 

 of the base ; dorsal margin more or less concave in outline, and showing 

 the usual lanceolate escutcheon margined on each side by a subangular 

 ridge ; hinge equaling about two-thirds the length of the valves ; lunule 

 rather small, deep, well defined, and narrow-subovate in form; beaks 

 moderately prominent, oblique, and placed about one-seventh the length 

 of the valves from the anterior end. Surface ornamented by small, 

 irregular ridges and furrows of growth. 



Length, 1.46 inches ; height to cardinal margin, 0.98 inch ; do. to hori- 

 zon of beaks, 1.03 inches; convexity, 0.66 inch; length of hinge, 1 inch. 

 Another specimen, 1.64 inches in length, has a convexity of 0.75 inch. 



It is quite possible that this may be only a variety of the last, but as 

 I have before me ten good specimens of that shell, and two of the form 

 under consideration, and there are among them no intermediate grada- 

 tions between the two forms, I can but regard them as distinct species. 

 The shell here described differs from the last, with which it was found 

 associated, in being proportionally decidedly shorter and wider (higher), 

 as well as in having its ventral margin much more prominent or deeply 

 rounded in the central region. Its beaks are also less oblique, rather 

 more prominent, and proportionally farther from the anterior end. It 

 shows some faint traces of a similar anterior oblique umbonal ridge to 

 that seen in the preceding species, but it is less distinct, and does not 

 show so decided a tendency to become angular at the beaks. 



Locality and position : Rushville, Ohio. Waverly group. 



GASTEROPODA. 



Genus PLATYCERAS, Conrad, 1840. 

 (Prelim. Report Palseont. N. Y., 205.) 



Platyceras (Orthonychia ?) LoDiENSE, Meek. 



Plate 13, figs, la, 6. 



Platyceras (Orthonychia?) Lodiense, Meek (1871), Proceed. Acad. Nat. Sci., Philad., 

 XXIII, 170. 



Shell rather small, non-spiral, or merely having the form of a rapidly 

 expanding cone, with a backward obliquity that brings the apex nearly 

 over the posterior margin ; lateral slopes nearly straight or slightly con- 

 cave, and converging to the apex at an angle of about 80° ; posterior side 

 vertical and decidedly concave in outline; anterior slope a little more 

 than twice as long as the height of the posterior side, moderately convex 



