142 
Kirtley F, Mather 
which is probably persistent as it occurs in each of the two 
apparently undistorted specimens of that valve which have been 
observed. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). Brentwood limestone: near 
Fayetteville, Arkansas (Station 134). 
Orbiculoidea missouriensis (Shumard) ? 
Plate VIII, figure 1. 
1858. Discina missouriensis. Shumard, Trans. St. Louis Acad. Sci., vol. 
1, p. 221. 
Middle Coal Measures: Lexington and Charbonnier, Missouri. 
1873. Discina nitida ? Meek and Worthen, Geol. Surv. 111., vol. 5, p. 572, 
pi. 25, fig. 1. 
Coal Measures: Illinois. 
1882. Discina Meekana. Whitfield, Ann, N. Y. Acad. Sci., vol. 2, p. 228. 
Coal Measures: Carbon Hill and Flint Ridge, Ohio; Illinois; Iowa. 
1884. Discina nitida. White, 13th Rep. Geol. Surv. Ind., p. 121, pi. 25, 
fig. 10. 
Coal Measures: Indiana; Illinois; Iowa; Missouri; abundant at 
Cannelton and Horse Shoe of Little Vermilion. 
1887. Discina Meekana. Herrick, Bull. Sci. Lab. Den. Univ., vol. 2, pi. 2, 
figs. 8, 9. 
Coal Measures: Flint Ridge, Ohio. 
18’87. Discina nitida. Herrick, Bull. Sci. Lab. Den. Univ., vol. 2, p. 145, 
pi. 2, figs. 8, 9. 
Coal Measures: Flint Ridge, Ohio. 
1888. Discina nitida. Keyes, Proc. Acad. Nat. Sci., Phil., p. 226. 
Lower Coal Measures: Des Moines, Iowa. 
1891. Discina Meekana. Whitfield, Ann, N. Y. Acad. Sci., vol. 5, p. 598, 
pi. 15, figs. 1-3; also p. 603. 
Coal Measures: Carbon Hill and Flint Ridge, Ohio. 
18’92. Orbiculoidea niUda. Hall and Clarke, Int. to Study of Brach., pt. 
I, pi. 5, fig. 16. 
Lower Coal Measures: Springfield, Illinois. 
1892. Orbiculoidea nitida. Hall and Clarke, Pal. N. Y., vol. 8, pt. 1, pi. 
4F, figs. 23-29. 
Coal Measures: Springfield, Illinois; Grover, Missouri, 
1894. Discina nitida. Keyes, Mo. Geol. Surv., vol. 5, p. 39, pi. 35, fig. 6. 
Coal Measures: Clinton, Lexington, and Richmond, Missouri. 
1895. Discina Meekana. Whitfield, Geol. Surv. Ohio, vol. 7, p. 483, pL 
II, figs. 1-3; also p. 488. 
Coal Measures: Carbon Hill and Hocking County, Ohio. 
