242 POTTS VILLE FAUNA OF OHIO 



lated; posterior dorsal margin rectilinear, very oblique; posterior ex- 

 tremity truncated, the margin nearly direct; beaks near anterior ex- 

 tremity; basal margin nearly straight in middle." 



This form is obviously very similar to A. vera and is probably 

 identical with the one which has previously been referred to the latter 

 species in various reports on the Pennsylvanian fauna of Ohio. How- 

 ever, the specimens examined by the writer .are narrower, with the 

 posterior-inferior angle less produced than is shown on Hall's figure. 

 These slight differences in outline together with more regular concen- 

 tric markings than are accredited to A. vera, seem to render identifica- 

 tion with A . concentrica more apt, although it does not seem improbable 

 that these species are the same and that the differences in outline and 

 surface markings are of varietal rather than of specific importance. 

 The form is convex and the beak is close to the anterior end, while the 

 surface is marked by about seventeen to twenty regular, sharply angu- 

 lar, concentric laminae, separated by broad furrows. The entire sur- 

 face is covered by very fine concentric lines. Faint radial stria tions, 

 such as are characteristic of the middle layer of shell substance of A. 

 varica, are often visible near the basal margin and are clearly marked 

 where the outer layer has been exfoliated. 



Several small, imperfect specimens from the Lowellville and Boggs 

 members have likewise been referred to this species, but the poorly 

 preserved condition of the material renders the identification more 

 doubtful. 



Dimensions. An individual of average size has the following 

 measurements: length 12 mm., height 11 mm., convexity of a left valve 

 5.5 mm. 



Horizon and locality. Lowellville member: Muskingum County, 

 Locality 19, r. Boggs member: Muskingum County, Locality 26, r. 

 Widely distributed throughout the Lower Mercer and McArthur mem- 

 bers, a. Upper Mercer member: Scioto County, Locality 59, c. Black 

 Flint member: Jackson County, Locality 87, r. 



Astartella newberryi Meek 

 PI. XIII, fig. 14 



1875 Astartella newberryi. Meek, Pal. Ohio, Vol. II, p. 340, PI. 19, Fig. 3. 

 Coal Measures: Newark, Ohio. 



Description. This fossil is present in the middle and upper Potts- 

 ville formation, but is especially common in the Lower Mercer limestone 

 of Muskingum and Licking counties. Although the species was origi- 

 nally founded on a single specimen, the characters attributed to it by 

 Meek have been found to hold constant in adult forms; it is almost im- 

 possible, however, to distinguish immature individuals from those 



